California Association of Criminalists
Since 1954
TRENDS IN THE PAINT INDUSTRY-IMPLICATIONS FOR THE FORENSIC EXAMINER
Darlene Brezinski, Consolidated Research, Inc.
The regulatory environment has significantly impacted the coatings industry and has caused tremendous change in the types of coatings being used today, the raw materials and the formulation of the coating. The result of these changes directly impacts on the analysis of paint particles, the interpretation of the data and the conclusions regarding the identification, nature and origin of the coating. An update on these trends, as well as the polymers and pigments that are being used will be reviewed, along with the impact the changes have on the forensic examiner. The focus will be on automotive coatings, but other areas will be included.
EVIDENCE MANAGEMENT IN A SERIAL HOMICIDE: PRIVATE LABORATORY PERSPECTIVE
Carol Hunter, California Laboratory of Forensic Science
Although evidence management in serial homicides may no longer be an uncommon issue, the impact of such a case containing thousands of evidence items is significant on a small private laboratory. Case approach decisions range from either doing a complete and thorough evaluation of all evidence or simply reevaluating the associative evidence. Restrictive lines of communication between the government lab personnel and private lab personnel complicated issues throughout the length of the case. Time consuming, complex evidence release and return mechanisms will be explained. Databasing the evidence became imperative for chain of custody, internal evidence control and eventual trial organization preparation. Maintaining the regular laboratory case load as well as serial case analyses became a balancing act. Issues regarding trial preparation for the attorneys will also be discussed.
PHYSICAL MATCH: A FOCUS ON ITS FORENSIC USE AND INTERPRETATION IN CRIMINAL CASES
Gary Cortner and John E. Hamman, California Department of Justice, Fresno Regional Laboratory
The concept of a physical match, or fracture match as it is sometimes called when referring to evidence, has long been considered a very powerful tool in the field of Criminalistics. To be able to conclude that evidence found at the crime scene and evidence associated with a suspect were at one time joined as one piece is indeed powerful evidence. Since the physical match is such a powerful tool, it is interesting that very little has been written defining exactly what criteria are necessary to achieve one. This presentation will show several published physical match comparisons as well as many that have been testified to in a court of law. Several definitions of a physical match will be discussed and attempts to create a physical match from non-physical matches will be shown.
DNA USERS GROUP MEETING
October 9, 1996
Morning:
Round Table Lab Updates:
DNA Advisory Board Update - Margaret Kuo / Mary Gibbons TWGDAM update, July meeting - Ken Konzak / Rob Keister National Institute of Justice, DNA Training Grant - Steve Lee FBI STR standardization project - John Hartmann CODIS update - Ken Konzak NRC II Report - John Hartmann
Afternoon:
Use of Statistics for Paternity Testing: Dr. Jeffrey Morris, Long Beach Genetics Recovery of the Products of Conception from Induced and Spontaneous Abortions in Rape and Incest Cases -- Don Johnson, LASD Paternity testing in criminal cases, casework experiences:
MICROSCOPIC FIBER IDENTIFICATION
Donald C. Felty, MicroSolutions
The most universal analytical tool available today is the light microscope and this is particularly true in the field of fiber examinations and identification. All it takes is a light microscope, an eye/brain combination and last, but not least, an interest in what you are doing, and with some experience a degree of excitement in realizing your own capabilities. The necessary instruments can be expensive but can also be purchased reconditioned with a great amount of savings. The ideal starting instruments would be a stereo microscope (approx. 10-40X) and a polarizing compound microscope (approx. 50-500X) with full and quarter wave plates, and a quartz wedge or compensator. You will also need a set or group of refractive index liquids, micro tools, reticles and other accessories, depending on your budget. Since natural fibers haven't changed and you can get help from the available literature, discussion will be mainly on man-made fibers where the manufacturers can and do make almost any conceivable shape or size fiber depending on customer request and end use of the fiber. With the ever changing nature of man-made fibers, one of the most essential forms of sample preparation is cross sectioning. Cross sectioning techniques, both very simple and more elaborate will be discussed along with the use of solvents, melting points and refractive index differences in identification.
Discussion will include some of the more difficult samples that you may encounter, such as: Fiber blends, bicomponent fibers, fibers containing voids and some of the newer R&D types of fibers that you can expect to see in the future. I hope that this discussion will make you want to try or retry the light microscope as a tool in fiber identification.
FORENSIC ODONTOLOGY
Gordon F. Freeman, DDS, Riverside, California
A forensic odontologist is a dentist with expertise in dento-legal matters, with dental investigations often leading to presentations in a court of law. There are two main areas in the field: 1. Unknown body identification, and 2. Bitemark analysis. This presentations' topic will include a brief history of forensic dentistry. Factors used in body identification and the methodology of the Department of Justice in dental comparisons will be discussed. Types of crimes involving bitemarks on human skin are to be reviewed, with emphasis on the legal value of well-defined bitemarks perpetrated during aggravated assaults.
HOW MR. PERSISTENCE LEFT HIS (TOOL) MARK: A TRACE EVIDENCE CASE INVOLVING A STABBING
Dean M. Gialamas, Los Angeles County Sheriffs Department, Scientific Services Bureau
A sixty-six year old man, distraught at his recent dissolution, was harassing his former girlfriend. After having received several threats, including bomb and stabbing threats, the girlfriend sought a court restraining order against her former boyfriend. Shortly after her motion was granted, the victim noticed her former boyfriend waiting for her outside her home. After confronting him, and stating that he was in violation of the court order just granted, her former boyfriend simply stated that there was "something" for her on her porch and quickly sped away in his truck. On the porch was a plastic doll and pink stuffed animal, both had been stabbed numerous times with a knife. A subsequent search of the suspect's residence and vehicle resulted in the recovery of a single-edged kitchen knife from his truck.
The author was assigned the task of determining if the recovered knife could have been involved in the stabbing of the items. Preliminary examinations showed that the doll and, to a limited extent, the stuffed animal had defects created by a single-edged instrument. The plastic polyethylene material of which the doll's body was made, had the ability to retain the instrument characters to a high degree: Not only could the instrument type be established as a knife, but also the dimensions of blade height and non-cutting edge width were easily measurable. Present on many of the defects to the doll were elastic reddish brown particles and/or smears. These "stains" were present on what would be the non-cutting edge of the knife used to create the defects. Examinations of the knife showed that it possessed the characteristics of the instrument used to cause the defects. The blade dimensions were similar. A reddish brown "stain" on the non-cutting edge of the blade was the same chemical composition as the "stains" on the defects to the doll. Furthermore, microscopic examination of the "micro-serrations" of the blade (as it was not a conventional serrated knife) showed pinkish material that was chemically similar to the polyethylene construction of the doll.
In this case an identification of the knife used in a stabbing was possible because of careful observations of trace evidence on both the instrument and the defects.
JELLYS SHOES: A NEW WRINKLE IN FOOTWEAR IMPRESSION COMPARISONS
Grant D. Graham Sr, Master Sergeant, U.S. Air Force Security Police
Robert D. Blackledge, Naval Criminal Investigation Service, Regional Forensic Laboratory Technology has produced highly pliable rubber compounds that are currently being used by shoe manufacturers to make shoe outsoles. Because the normal outsole pattern made by such a pliable rubber can undergo bending and contortion when subjected to kicking, twisting and/or turning motions while being worn on the human foot, the shape of the pattern can change with the direction of force applied. If the shoe's outsole surface contains sufficient individualizing characteristics it can be likened to the individual ridge patterns of a person's fingerprint. Even though a fingerprint can be contorted by direction of force, the ridge pattern remains the same and can still be used to conclusively identify a person. This study contends that the same principle can be applied to contorted footwear impressions, providing there are sufficient individual characteristics present.
Pairs of known shoes with rubber outsoles ranging from very pliable to stiff, were subjected to forces at various angles (vertical, horizontal, acute/obtuse left and right) and various twisting/turning motions to test the above theory. The results of the tests will be presented along with their implications to footwear impression comparisons.
HORNADY VECTOR AMMUNITION: AN UPDATE ON A NEW TOOL IN STUDYING SELECTED EXTERIOR AND TERMINAL BALLISTIC EVENTS OF FORENSIC INTEREST
Lucien C. Haag, Criminalist Forensic Science Services, Carefree, AZ
A new product introduced in 1994 by the Hornady Manufacturing Company of Grand Island, Nebraska offers a unique opportunity to safely study and illustrate a number of exterior and terminal ballistic events of forensic interest. Bullet ricochet after low angle impact with a variety of surfaces, bullet precession and stability after ricochet or impact with intervening objects are all examples of events that occur in shooting incidents which have been studied with considerable difficulty and substantial investments in time and equipment. With this ammunition and the use of appropriate photographic equipment, the pre- and post-impact behavior of these bullets can be recorded and studied. Initially this product was only available in a 115gr. FMJ 9mm loading. It has since been expanded to include 40S&W and 45ACP along with a heavier loading in 9mm Parabellum. These new products allow for various exterior and terminal ballistic intercomparisons to be made between these popular pistol calibers;
"RUBY RIDGE REVISITED": THE BALLISTICS EVIDENCE AND ISSUES
Lucien C. Haag, Criminalist Forensic Science Services, Carefree, AZ
The Weaver case which took place in northern Idaho in the late summer of 1992 resulted in the shooting deaths of deputy U.S. Marshal William Degan, the 14 year old son of white supremacist Randy Weaver, his wife, Vicki Weaver and their dog, Striker. These events lead to an unsuccessful prosecution of Randy Weaver and Kevin Harris for the murder of Billy Degan.
The Weaver case subsequently became the subject of the considerable debate, civil litigation with a multimillion dollar settlement in favor of the Weavers, congressional hearings, T.V. network presentations, news magazine articles, at least one book and possible additional litigation yet to come. This case has also changed the way many Americans view their freedoms, their values, and their government. The trail up to Ruby Ridge led to an Old West gunfight, four deaths and the invasion of a remote county in northern Idaho by and army of state and federal agents. It channeled America's deepest insecurities and drew thousands of people into a whorl of fear and stubbornness, mistakes and misjudgments, lies and a cover-up that ultimately shook the top levels of several federal agencies. More even than the deaths at Waco, the Weaver standoff has brought paranoia into the mainstream. For many otherwise normal and average citizens, it has become a symbol for government tyranny.
But symbols fall well short of explaining a place as hard and remote as Ruby Ridge. From this jagged point, the Weaver case is not proof of broad government oppression and tyranny, but of human fallibility and inhuman bureaucracy, of competitive law enforcement agencies and blind stubbornness. The Randy Weaver case is a stop sign, a warning - not of the danger of right-wing conspiracies or of government conspiracies - but of the danger of conspiracy thinking itself, by people and governments. Forensic scientists can and should have a public voice in setting the record straight regarding certain aspects of this and other like cases.
Except for the criminal trial in 1993, virtually all of the information regarding the positions and movements of the various shooters and gunshots victims, the nature of the gunshot wounds sustained by the victims and the location of key items of physical evidence has been taken from the surviving participants. Indeed, some overlooked and "new" physical evidence was only recovered recently (1995) and examined by the presenter. During the Fall 1995 Senate -Subcommittee hearings several new issues and theories regarding the events at the two shooting scenes were put forth. For example - It was suggested that a fellow U.S. Marshal, not Kevin Harris, shot Deputy Marshal William Degan during the initial shoot-out and that Randy Weaver accidentally shot his own son during the same engagement at a place known as the "Y". This presentation will illustrate the various ballistic events that took place at the "Y" on August 21, 1996 and at the Weaver cabin the following day.
THIS HAIR IS RARE
Lynne D. Herold, Los Angeles County Sheriff's Department, Scientific Services Bureau
Several case examples will be presented in which rarely encountered microscopic hair characteristics were observed in human hairs including unusual medullary structure, banding patterns associated with body decomposition, evidence of insect activity along the hair shaft, unusual ovoid body size and position, and odd hair coloration.
TWGMAT- WHAT IT IS, WHAT IT'S DONE, WHAT IT DOES AND WHAT IT WANTS TO DO
Lynne D. Herold, Los Angeles County Sheriff's Department, Scientific Services Bureau
The Technical Working Group for Materials Examination, otherwise known as TWGMAT, is the currently active working group for the examination of polymeric materials. Historically, this group began as TWGFIBE (fibers) and evolved into TWGMAT with the addition of paint and glass groups. The objectives of TWGMAT are to provide a means for the exchange of information to the forensic community, to review current research in order to assess the status of the technology, to perform collaborative studies, and to produce guidelines for materials examination. Currently, TWGMAT participants include forensic scientists from public, private, and international laboratories, and representatives from NIST and private industries. In June of 1996, the TWGMAT produced Guideline for QA/QC General Materials was introduced for review. Operational sub-committees are concurrently working on producing scientific literature bibliography data bases, materials data bases, and scientific information data bases.
PORTABLE SAMPLER FOR COLLECTING ACCELERANT FROM FIRE DEBRIS
W.K. Johnston, Ph.D., Chemical Consultant Services
An essential step in determining that a fire was caused by arson is demonstrating the presence of a flammable fluid in debris collected from the fire scene. Although metal cans have been used for over twenty years, far better methods for preserving arson evidence have been developed based on technology developed by the Army for characterizing residue from chemical nerve agents. A portable sampler is described which can be used in the laboratory or carried to a fire/bomb scene. The sampler contains a Teflon lined, sealed chamber. The chamber is heated and vapors drawn through a charcoal trap using a vacuum pump. Residue from floor drains and surfaces can be collected by inverting the sample chamber over the contaminated area. Sealed, contaminant free, charcoal traps are available from Supelco, SKC, and other sources. After sample collection, the trap is removed and further preserved by sealing it in a glass vial for shipment to the laboratory. The small size of the trap, 1/4" X 2 1/2", makes shipping convenient. Investigators also avoid the problems of carrying bulky metal cans in their vehicles. Valuable evidence is not lost in opening a metal can in the laboratory. Accelerant is separated from other debris as soon as possible further assuring its preservation. Laboratory storage space is conserved.
Once in the laboratory a glass wool plug is removed from the end of the adsorbent tube. The charcoal or other adsorbent material is emptied into an auto sampler vial for analysis by capillary gas chromatography. Evidence can be analyzed over night using auto samplers. For special applications where the highest level of sensitivity is required thermal desorption tubes can be used. With thermal desorption all of the accelerant trapped in more than 500 grams of debris can be focused on the head of a GC column for a single analysis.
IMPROVISED EXPLOSIVE DEVICES OF A SUBURBAN TERRORIST: NOT YOUR ORDINARY RUN-OF-THE-MILL PIPE BOMBS
Gregory E. Laskowski, BS, MPA, Kern County District Attorney, Forensic Science Division
This paper will describe the events which lead to an explosion that rocked a sleepy southwest Bakersfield neighborhood in the early morning hours of February 9th, 1996. The suspect in this case was arrested at the scene after he had attempted to shoot at a police officer, and set fire to his van in a somewhat unsuccessful self-immolation attempt. As a result of the explosion which destroyed the van and a nearby apartment complex, an intense investigation lead to the recovery of remains of the explosive devices and bomb making literature. This literature identified several key components of homemade high explosives as well as the recipes for the manufacture of the boosters charges and main charges. While the devices were primarily Ammonium Nitrate/Fuel Oil (ANFO) bombs, the boosters included nitromethane with naphthalene and hexamethylenetriperoxidediamine (HMTD). These materials and their precursors are readily obtainable and relatively easy to make. The ramifications of the availability of many household materials in the hands of the "urban terrorist" will also be discussed.
THE IDENTIFICATION OF A BULLET TO A FIREARM USING A BARREL CAST
Gregory E. Laskowski, BS, MPA, Kern County District Attorney, Forensic Science Division
The comparison of a fired bullet to a barrel cast in cases where the barrel has been altered is described. It is possible to cast a gun barrel with a suitable casting material such as Mikrosil ™ and obtain a suitable mirror image of the interior of that barrel. In many respects, a barrel cast will simulate a fired bullet such as a test fire. One must bear in mind that the cast will not reflect all the markings or striae found on a test fired bullet at the appropriate places. There are, however, some instances where sufficient markings in both the groove and land impressions are available to compare to an evidence bullet. If such is the case, then an identification can be made.
This paper will describe the comparison of two spent evidence bullets to a Mikrosil™ barrel cast of a Colt .25 Caliber semiautomatic pistol which had been subjected to mechanical alteration. In addition, a validation study will be described in which a barrel cast was taken from a laboratory reference specimen, a Colt .32 Hammerless, Rimless semiautomatic pistol of the same vintage and compared to test fired bullets from that firearm.
MAXIMIZING CAPILLARY GC COLUMN LIFE
Al Madden, Applications Chemist, J & W Scientific
Gas chromatography is a commonly used tool for the identification of fire accelerants. Capillary column performance can be maximized with proper installation and sample handling. This ensures optimal resolution and chromatographic efficiency. Even with proper operation, sample residues can impair the column's retentive properties and inertness. Topics covered will include removing sample residues, preventing contamination, and troubleshooting tips for a gas chromatograph equipped with a flame ionization detector. With these concepts, the chromatographer will be able to determine the causes and understand the tools to solve these chromatographic problems.
COORDINATION OF A HIGH PROFILE FORENSIC SCIENCE CASE: PEOPLE VS. SIMPSON
Greg Matheson, Los Angeles Police Department
Every criminal and civil investigation involving the forensic sciences requires some level of overview and coordination. From the simplest one item narcotics case to a multi-victim serial murder case, the criminalist must assess the information, determine proper analytical schemes, and ultimately provide the trier of fact with complete and impartial data. The complexity of coordinating the forensic science aspect of an investigation is affected by many factors: The seriousness of the crime, the quantity and quality of the evidence, the number of victims, and unfortunately, the interest of the public. The usual tasks of determining what evidence to analyze, what analytical schemes to follow, meeting all Discovery obligations and preparing for testimony becomes more difficult when dealing with a high profile case. As the coordinator of laboratory activities in the criminal case of the People vs. Simpson, it was also necessary to track evidence-being transported to several outside laboratories, interact with a multitude of attorneys on all sides of the case, and deal with the immense level of stress and tension, both personally and on all of the laboratory staff. Accusations of being the source of media leaks resulted in the LAPD Crime Lab not being allowed to know the results of testing performed by outside laboratories. All of these tasks were expected of the laboratory, while attempting to maintain the regular flow of cases that continued unabated.
This presentation will focus on the coordination of laboratory involvement in the case of People vs. Simpson. Due to the current civil litigation and associated gag order, there will be no discussion of specific evidence items or opinions associated with the evidence, its collection or analysis.
THE POLLY KLAAS KIDNAPING INVESTIGATION; FBI SAN FRANCISCO'S NEW "CHILD KIDNAPING TASK FORCE"
Supervisory Special Agent Gordon G. McNeill, Federal Bureau of Investigation
This talk will cover:
THE MOTT ROAD HOMICIDE
Bruce Palmer, California Department of Justice, Redding, CA
The body of an adult white male was discovered lying on a paved road. The reconstruction of the crime scene will be demonstrated through slides of the scene and a discussion of blood spatters, blood patterns, body position, wound morphology and associated evidence.
COMPARISON OF FLUORESCENCE DETECTION OF THE GENEPRINT™ POWERPLEX™ STR SYSTEM BY OPTICAL SCANNERS AND DNA SEQUENCERS
Sherrie Post*, Steven Lee*, Tamyra Moretti**, James Robertson**, and Bruce Budowle**
*Califomia Dept. of Justice, DNA Laboratory; **F.S.R.T.C., FBI Academy, Quantico, VA
The GenePrint™ Powerplex™ STR System (Promega Corp.) is a short tandem repeat multiplex system consisting of two quadruplexes (8 STR loci) that are amplified in one tube. The primers for the loci CSF1PO, TPOX, THO1, and vWA (CTTv) are labeled with the fluorescent dye tetramethylrhodamine and the primers for the loci D16S539, D7S820, D13S317, and D5S818 (D16, D7, D13, D5) are labeled with fluorescein. Detection of the products can be achieved either by scanning a slab gel post-electrophoresis or by real-time scanning during electrophoresis and performed by the DNA sequencer. Due to differences between instruments in the ability to detect the two dyes, Powerplex kits with different concentrations of labeled primers have been developed to optimize signal detection on the DNA Sequencers 373/377 (Applied Biosystems Div., Perkin-Elmer), and the FMBIO 100 (Hitachi Software Engineering). The performance of a Powerplex™ beta test site kit was examined on each of the instruments listed. A series of experiments were carried out that involved variation of the template concentration, temperature of annealing and Mg2+ concentration. In general, the loci appear to be balanced and there were minimal shadow bands (stutter). The performance of THO1 and vWA in the Powerplex system was improved over that of the same loci in the original GenePrint™ Fluorescent STR System, because THO1 exhibited a much higher signal intensity in the new system, and stutter at vWA was dramatically reduced. Using the 373 DNA Sequencer and 6% PAG to analyze the PCR products, the signals for the loci were fairly similar in intensity across the loci, except that the signals of some of the loci were more intense than those for D16S539. A major problem with the test configuration was that the signal intensity of CTTv products was significantly lower than the intensity of the D16, D7, D13, D5 products. When using the Hitachi FMBIO 100 to analyze the PCR products, the intensity of CTTv products was consistently higher than the intensity of the D16, D7, D13, D5 products, and the signal of D13S317 was slightly lower than the other loci within its quadruplex.
In summary, the Powerplex seems to be a useful set for obtaining a lot of data from one PCR, and the products can be analyzed on a variety of fluorescence detection systems.
CHARACTERIZATION OF D1S80 HETERODUPLEXES
R. Reynolds, Ph.D., S. Cosso, Roche Molecular Systems, Inc.
The majority of D1S80 alleles have between 14 and 41 repeat units and migrate with the same mobility as the corresponding alleles in the AmpliFLP D1S80 Allelic Ladder. D1S80 alleles with greater than 41 repeat units have been observed and confirmed by Southern analysis. In addition, off-ladder alleles have been observed. Several off-ladder variants have been sequenced and compared to corresponding alleles in the allelic ladder. We found that sequence differences within the repeat units account for the mobility differences.
In addition to these well-characterized bands on D1S80 gels, two other types of bands have been observed by analysts in nearly all laboratories using this marker system. First, extra bands have been observed in the size range of the allelic ladder that do not line up with the ladder bands. Second, there are bands that migrate much higher in the gel than the allele-41 band in the ladder. Some of these bands are non-specific PCR products, but frequently the bands are due to hereroduplexes. We have analyzed heteroduplexes that migrate as a single band and others that migrate as two bands. We also investigated the effect of repeat unit sequence on heteroduplex formation. Based on these studies, we concluded that for some samples it may be necessary to do additional testing to ensure that D1S80 results are interpreted correctly. We developed a simple test for distinguishing heteroduplexes using a novel approach.
MITOCHONDRIAL DNA ANALYSIS OF >600 INDIVIDUALS FROM 4 POPULATIONS USING A RAPID, SENSITIVE IMMOBILIZED SSO PROBE TYPING SYSTEM
R. Reynolds, Ph.D., M. Grow, B.S., J. Varlaro, B.S., M. Alavaren, E. Clark Ph.D., T. Marschak, B.A.; Roche Molecular Systems, Inc.
Mitochondrial DNA (mtDNA) has unique features that make it a particularly useful target for the analysis of telogen hairs, missing person and mass disaster remains, and biological samples that are too small or degraded to be analyzed by nuclear DNA markers (e.g. AmpliType PM, HLA, DQA1, D1S80, STRs). First, based on numerous studies on populations around the world, the mitochondrial genome is very polymorphic both within and between population groups. A second unique feature of the mitochondrial genome is that each cell contains 1,000-10,000 copies. Finally, mtDNA is inherited matrilineally so that maternally related individuals can serve as a reference for missing persons.
Several laboratories are using DNA sequence analysis for typing mtDNA, but this approach is very time consuming and costly; Consequently, most forensic laboratories will find it impractical to implement mtDNA sequence analysis, and a large number of probative samples will not be analyzed unless they are sent to an outside laboratory. To address the need for a faster, less expensive method for mtDNA analysis, we have developed a typing system using AmpliTaq Gold DNA polymerase to provide highly specific and robust PCR amplification of the hyper-variable II (HVII) segment in the control region of mtDNA. The 422 base pair HVII PCR product is typed in less than two hours using fourteen sequence-specific oligonucleotide (SSO) probes immobilized on a single strip. The ability to distinguish individuals using this mtDNA typing system has been estimated from mtDNA sequence databases; it is comparable to HLA DQA1, which has a power of discrimination value of ~0.95. We have typed mtDNA isolated from a total of 617 unrelated U.S. Caucasian, African-American, U.S. Hispanic, and Japanese individuals to obtain frequency data for the HVII region directly. We also determined the number of unique "mitotypes" detected in these population groups by this panel of fourteen SSO probes. We determined that this typing system effectively discriminates between individuals, making it useful not only as a screening tool for sequencing, but also as a stand-alone test.
COMPUTER STATISTICAL ANALYSIS OF MIXED STAINS IN THE CASES OF RAPE
Prof. Sergei Grishechkin*, Dr. Ksenia Prokofjeva*, Dr. Irina Perepechina**
* Moscow State University, Moscow, Russia
** Center of Criminalistics, Ministry of the Interior, Russia
One of the most difficult cases on practical applications of DNA fingerprinting is the so-called mixed stains cases, when an evidentiary sample contains DNA from more than one contributor. This is typical for rapes. Statistical analysis in such situations becomes very cumbersome and is out of hand for practitioners because many different variants exist, especially if the victim has died. In these cases, the number of contributors is not known precisely and you should investigate all possible variants in order to choose the one which is the most favorable to the suspect. The same concerns the situation in which it is not known explicitly whether the victim has contributed to the stain or not.
We present a computer software package "Grape" (for MS Windows 3.1 or higher) which performs all statistical computations involved in these types of cases. Grape supports both of the approaches presented in the 1992 and 1996 National Research Council Reports. Grape automatically analyzes all possible variants, selects the most favorable for the suspect and prepares the final document with the match probability or likelihood ratio. Grape has a library of available loci which can be used for the calculations.
PAINTS AND COATINGS AS TRACE EVIDENCE
Scott Ryland, Florida Department of Law Enforcement, Orlando Regional Crime Laboratory
Paint is a pigmented liquid which is converted into an opaque solid film when applied as a thin layer. It comes into the forensic science laboratory in a variety of types, including automotive, architectural, maintenance, marine, and aircraft paints. Hit-and-run with death or injury incidents are the most common and typically involve cured multi-layered automotive coating systems. They are either of a comparative nature, if a suspect vehicle has already been acquired and appropriate standard samples taken, or of a classification nature, if the examiner is asked to attempt to identify from what type of vehicle the questioned paint originated. Automotive paint may also be transferred onto a homicide victim's clothing while being transported from the scene to a disposal site and, like automotive textile fibers, may ultimately be discovered in the trace debris adhering to the surface of clothing. Architectural paints are routinely encountered in cases involving forced entry into a dwelling or business. Cases range from property crimes to sexual assaults and homicides. Paints may be abraded onto a tool used to gain entry, flaked onto clothing while climbing across a painted surface, or transferred to a homicide victim's clothing while being dragged across a painted floor. Maintenance paints are found as original coatings on tools and are thus prone to cross transfer in forced entry cases. Attentive medical examiners might also discover them in blunt trauma wound tracts. They find their way into the laboratory in surprising forms, such as bridge paints, mirror backing coatings, spray paints coating homicide victim's bodies, and even fingernail polish. Marine and aircraft paints are less frequently encountered, but may be involved in drug smuggling investigations, water vehicle accidents, or aircraft crash investigations. Forensic coatings specimens are usually small, cured, multi-layered paints demanding careful choice of analytical techniques to maximize discrimination potential while conserving sample for subsequent examiners. Major paint components of each individual layer are of concern. The approach used by a majority of laboratories in the United States includes a thorough microscopic characterization followed by FTIR spectroscopy and SEM/EDX analysis of the individual layers present in the samples. These techniques may be augmented (or replaced) by others, including pyrolysis gas chromatography (PGC or PGC/MS), XRF spectrometry, and x-ray diffractometry. Coatings classifications impart credibility to testimony, characterize end-use of the specimens encountered, and aid in accessing data base compilations. Coatings comparisons focus on discrimination between sources. One must keep in mind that they re only as good as the acquired case standard samples. Though all would like to use every technique available to maximize discrimination power, today's practical constraints of tighter budgets and requirements to improve turn around times demands we seek the more modest path of identifying dependable ways to differentiate most, if not all, forensically encountered paint exemplars.
WORLD WIDE WEB HOMEPAGING: CONSIDERATIONS FOR CRIMINALISTS
Ray Silvia, Josh Spatola, Jessica Sazaki, California Department of Justice, California Criminalistics Institute
The World Wide Web is undergoing explosive growth because of its increasing usefulness and its relative ease of use. After learning how to navigate the web, the next step often involves an individual's or organization's decision to develop and to place one's own homepage on the web.
The California Association of Criminalists (CAC) is no exception. In 1995, for example, Peter Barnett created the CAC Homepage. This July, the CA DOJ Riverside Lab, hosting this CAC 1996 Fall Seminar, also utilized a homepage, which has proven an effective means of advertising the Seminar to criminalists, to vendors, and to other interested persons worldwide.
Our presentation will include the following:
TRACE EVIDENCE IN THE SUFF MURDERS; CALIFORNIA'S NEWEST CONVICTED SERIAL KILLER
Faye A. Springer, Sacramento County Crime Laboratory
From 1988 to 1991, Bill Suff abducted prostitutes and drug users and subsequently murdered them. He disposed of their bodies in the rural areas of Riverside County. This paper will discuss how trace evidence was used to link these victims to a common serial killer.
The trace evidence removed from the victim's bodies was developed into investigative leads which assisted in the identification of the suspect in late 1991. Twenty bodies were examined, out of which thirteen charges of murder were eventually filed. The difficulties in organizing and comparing large amounts of trace particles and fibers between bodies with the intent of providing investigative leads to law enforcement will be discussed. During the time of the murders, Suff lived in eleven residences and drove four different vehicles. Reference samples from most of these locations and vehicles were eventually compared to the trace from all of the victims' bodies. The organization of comparisons to these reference samples after Suff was arrested will be discussed.
The testimony describing hair, fiber, and paint comparisons took six days. Suff was convicted in twelve out of the thirteen cases, with the remaining case ending in a mistrial because of a hung jury.
VALIDATION OF THE PROFIBLOT II TEMP AUTOMATED STRIP PROCESSOR FOR DQA1 AND PM TYPING
John Tonkyn Ph.D., Armand Tcheong, B.S., and Steve Lee, Ph.D., California Department of Justice, DNA Laboratory
DQA1 and Polymarker (PM) reverse dot blot typing (Roche Molecular Systems) requires significant amounts of "hands-on" time for strip processing. The Profiblot II Temp automated strip processor (SLT Instruments) automates the steps of probe hybridization, binding of enzyme conjugate and color development, as well as all of the intervening wash steps. Validation of this instrument for use in both databanking and forensic casework according to TWGDAM guidelines was performed. In addition to validation results, preliminary results on the use of this instrument for typing mitochondrial DNA with reverse line strips is presented.
For each relevant section of the TWGDAM guidelines (Section 4.5), automated processing was performed with both DQA1 and PM strips. These included determining sensitivity, typing known samples, nonprobative case samples and mixed samples. In addition, precision (reproducibility) was evaluated for both typing results and temperature. The sensitivity was similar to manual typing, with the PM S dot being detected at 0.25 ng input DNA and the DQA1 C dot being detected at between 0.1 and 0.25 ng. No cross hybridization was detected in either system up to 50 ng. Using DNA mixtures, the minor component could be detected at 1:10 to 1:20 ratios with PM, and from 1:10 to 1:100 with DQA1, depending on the allele. Temperature accuracy and precision, both within a well and throughout the 24 well tray was evaluated. No significant temperature variation across the tray was detected using a dual-thermocouple NIST-traceable electronic thermometer. Tray temperature was within the window of 55.0° C +/- 1° C required by the protocol (often within 55.0° C +/- 0.5° C). Typing was very reproducible between wells and between runs. No cases of contamination were detected using this instrument, either by spill over between wells or by carryover by the aspiration tips.
These results indicated that Profiblot II Temp automated strip processor is a valid instrument for both DQA1 and PM Typing. All automated typing results produced the same genotypes as manual typing. However, robotic processing results varied slightly from manual processing in two ways: 1) Slightly stronger PM signal occurred in the right end of the tray, but this did not alter the interpretation of results, and 2) Robotic aspiration failed in 1.7% of the strips processed (9 of 544). This causes liquid to not be drained from the well and depending on the particular step, can lead to either a high blue background or to no signal.
IMPROVEMENTS TO PROTOCOLS FOR DIFFERENTIAL LYSIS AND EXTRACTION OF SEXUAL ASSAULT SAMPLES
J. Varlaro, BS, R. Reynolds, Ph.D., Roche Molecular Systems, Inc.
DNA typing results that show a mixture of two or more DNAs can be difficult to interpret. Recent advances in DNA typing using automated gel-running/scanning platforms can facilitate the interpretation of mixtures. The instruments can quantitate signals from labeled or stained PCR products to determine if the allele signals are balanced; an imbalance in the allele signals can indicate the presence of a mixture of DNA from two or more individuals. Signal quantitation can be used to try to distinguish the various contributors to the sample. While the ability to quantitate signals may give an analyst more confidence in his or her conclusions, the interpretation of mixtures will always be open to attack by the opposing side. In addition, the frequencies obtained from mixtures are considerably less significant than those obtained from unmixed samples, even when the mixture can be "sorted". Lower frequencies affect not only the significance of results presented in court but also the number of samples that can be searched in state and national databases. Therefore, our goal is to minimize the number of extracted samples that contain detectable mixtures of DNA.
The overwhelming majority of forensic samples that contain mixtures are from sexual assault cases. These samples typically contain epithelial cells (E. cells) from the victim and sperm cells from the assailant(s). The standard procedure for preparing this type of evidence for DNA typing is to perform a differential lysis of the cells followed by extraction of the DNA. The differential lysis preferentially lyses the E. cell DNA and with repeated washing of the sperm pellet, the sperm cells are then lysed to release their DNA. The enriched fractions can then be analyzed using a variety of DNA typing tests. Sometimes the fractions are not completely separated and the E. cell DNA type can be detected in the sperm fraction. A high E. cell to sperm ratio can lead to carryover of enough E. cell DNA to be detected in the sperm fraction, even after extensive washing of the sperm pellet. We have investigated a variety of procedures for removing the residual E. cells and/or E. cell DNA from the sperm pellet, including treatment of the washed sperm pellet with DNase I (originally proposed by George Herrin of GBI). We will present results obtained from both mock and real sexual assault samples.
