114th SEMI-ANNUAL SEMINAR (Fall 2009)
CALIFORNIA ASSOCIATION OF CRIMINALISTS
October 26-30, 2009
San Jose, CALIFORNIA
THERMAL DESORPTION USING TENAX™: AN ALTERNATIVE TO THE ACTIVATED CHARCOAL STRIP FOR REMOVAL AND CONCENTRATION OF IGNITABLE LIQUID RESIDUES FROM SAMPLES OF FIRE DEBRIS
Eamonn McGee, Centre of Forensic Sciences
The forensic identification of ignitable liquid residues in samples of fire debris is typically achieved by analysis of headspace vapors from the sample container, using a Gas Chromatograph coupled to a suitable detector such as a Mass Spectrometer (GC-MS). The headspace vapors are adsorbed onto a suitable substrate and then introduced onto a capillary GC column where the analytes of interest can be separated and identified. The most common technique uses an activated charcoal strip as adsorbent with subsequent solvent elution of the trapped compounds. 90% of the labs that participated in a recent forensic flammables proficiency test used the activated charcoal strip method. The other participants used Tenax (6.3%) or Solid Phase Micro Extraction (SPME) fibres (3.7%) as the adsorbent, with subsequent elution using thermal desorption. Tenax is a hydrophobic porous polymer resin that preferentially adsorbs organic vapors. Sampling tubes containing Tenax are thermally desorbed in a dedicated instrument whereas SPME fibres such as polydimethylsiloxane are desorbed in the injection port of a gas chromatograph.
Thermal desorption is widely used to monitor and identify volatile compounds in both the environmental and occupational health and safety fields. The technique tends to be overlooked by forensic laboratories in the United States even though it is successfully applied to the identification and classification of ignitable liquid residues in Canada, Australia and Europe. This presentation will describe the analysis of headspace vapors from fire debris samples using automated two-stage thermal desorption coupled with gas chromatography-mass spectrometry (ATD-GC-MS). This analysis scheme, using Tenax TA as adsorbent, has been in use at the Centre of Forensic Sciences (CFS) for two decades. The advantages of thermal desorption, including fast sampling times, no solvent interference and automated analysis will be discussed as well as limitations such as preferential adsorption. The results of a recent in-house study at CFS demonstrating the usefulness of ATD-GC-MS for screening debris samples for oxygenated solvents such as acetone and isopropyl alcohol will also be presented.
DEVELOPMENT OF THE POWERPLEX® 16 HS SYSTEM
Yasser Daoudi, Promega
Short tandem repeat (STR) analysis remains the primary method for human identification. Forensic typing, criminal databasing and relationship testing laboratories in the US and many other regions of the world use a standard set of 13STR markers selected by the US Federal Bureau of Investigation for the Combined DNA Indexing System (CODIS). The PowerPlex® 16 HS System co-amplifies these 13 loci (D18S51, D21S11, THO1, D3S1358, FGA, TPOX, D8S1179, vWA, CSF1PO, D16S539, D7S820, D13S317 and D5S818) plus the low-stutter Penta E and Penta D markers and the gender-determining Amelogenin locus. One primer for each of these loci are labeled with fluorescein, carboxy-tetramethylrhoamine (TMR)or 6-carboxy-4',5'-dichloro-2',7'-dimethoxy-fluorescein (JOE). Amplicon size is determined by comparison with the Internal Lane Standard 600 (ILS 600) labeled with carboxy-X-rhodamine(CXR). This four-color chemistry can be analyzed on the ABI PRISM® 310, 3100 and 3100-Avant Genetic Analyzer sand Applied Biosystems 3130 and 3130xl Genetic Analyzers using existing dye matrix standards. The PowerPlex®16 HS System provides a hot-start Taq DNA polymerase in a modified master mix to provide increased ease-of-use and performance over previous PowerPlex® systems. This assay has increased tolerance to common forensic sample inhibitors known to reduce genotyping success rates. The presentation will share results from sensitivity and inhibitor studies along with developmental validation results.
O BROTHER WHERE ART THOU? A CASE OF FAMILIAL IDENTITY
Pamela, Hofsass, San Francisco Police Department
In November 2005, a prostitution deal went very wrong when 2 suspects blindfolded and kidnapped 2 victims in San Francisco and took them to a motel in a different city to rape and rob them. A third suspect was picked up on the way to the motel and also joined in on the assaults. The case was cracked through stolen cell phone records and assistance from outside agencies for two of the three assailants. Several items of evidence collected from the SAEKs linked suspect #1 and suspect #2 to each victim. A third unknown male profile was detected and reported by the crime lab but no further leads were established at the time of the initial investigation. A preliminary hearing for defendants #1 and #2 provided more information on the third assailant. A request was made to investigate the possible connection between the third unknown male and suspect #2. A familial match was discovered through careful consideration of the DNA results. A search warrant was granted for the reference DNA of suspect#2's younger brother, who coincidentally joined the Armed Forces when his older brother was arrested. Upon the match of all 13 markers from the evidence to victim #1, an Arrest Warrant was issued and with the assist of NCIS, an arrest and extradition of the younger brother of defendant #2 occurred. Eventually, all three defendants were held to answer. This presentation will describe the investigation from start to finish and provide some insight into the trials and tribulations of a sex crimes detective.
A NATIONAL ETHICS CODE FOR FORENSIC SCIENTISTS
Peter Barnett, Forensic Science Associates
The National Academy of Sciences' (NAS) report, Strengthening Forensic Science in the United States: A Path Forward, calls for the development of a national code of ethics for forensic sciences. A draft of such an ethics code has been developed by an ad hoc committee of the California Association of Criminalists based on review of large number of ethics codes of various forensic science organizations. The initial version of this document was presented at the CAC Seminar in May. Since then the committee has refined the code, simplified it, and published it at the ASCLD meeting in August and on the CAC web site. The current draft of the ethics code will be presented for review and discussion. Meeting attendees are encouraged to share the document with members of their laboratories and encourage them to send comments to the committee at firstname.lastname@example.org. Further review of this document is anticipated at a workshop at the February, 2010, AAFS meeting. The final result of this process will be a consensus code of ethics which can serve as the national code of ethics called for in the NAS report. Mr. Barnett would like to recognize his co-authors on this project: Carolyn Gannett, John Murdock, Hiram Evans, Jeff Thompson, James White, Peter DeForest, and Jasmine Jefferson
RELATIONAL EVIDENCE - SPECIAL COLLECTION AND "REASSEMBLY" OF SHOEPRINTS FROM A CRIME SCENE
Cordelia Willis, Santa Clara County DA's Crime Laboratory
Relational evidence requires special consideration when processing crime scenes -- when this evidence cannot be collected in such as way as to directly demonstrate its relational nature, the collection techniques used must allow for the relationships between items to be reassembled later. This presentation will discuss a crime scene where shoeprint evidence was collected in this manner. The layout of dusty shoeprints in a foyer (leading from the front door to the homicide victim) could not be collected via photography, so the overall relationships between shoeprints could not be assessed directly. Instead, the evidence was collected with numerous overlapping electrostatic dust lifts; these lifts were preserved via photography and then "reassembled" back at the lab (using crime scene photographs and tile lines) to produce a nearly complete map of shoeprint evidence in the foyer.
FIREARMS IDENTIFICATION - UNDER THE GUN -REVIEW AND RESPONSE TO RECENT CRITICISMS
Andy Smith, San Francisco Police Department Crime Laboratory
Within the last few years firearm and toolmark identification has come under increased scrutiny and criticism from academics, legal challenges, and government funded studies. This presentation will briefly outline these criticisms as well as look at the response from the firearm and toolmark examiner community. It is incumbent for all firearm and toolmark examiners as well as forensic scientists in general to be aware of any criticism or debate that swirls around their discipline. Although the presentation is geared more directly at firearm and toolmark examination, it is hoped that the basic tenets laid out will be applicable to many other disciplines within forensic science, especially the comparative sciences.
A DISCUSSION OF THE UNITED STATES SUPREME COURT MELENDEZ-DIAZ DECISION
Michael Chamberlain, Deputy Attorney General, California Department of Justice
In June 2009, the United States Supreme Court decided Melendez-Diaz v. Massachusetts (2009) 129 S.Ct. 2527. This case held that affidavit-style laboratory reports are not admissible as evidence without "the analyst" being subject to cross-examination in court. Deputy Attorney General Michael Chamberlain will discuss what this holding means for California criminalists and crime lab managers. Does it mean that the actual analyst(s) who did the bench work must go to court? Does it mean that analyst can offer expert opinions based on another (absent) analyst's report? How have the California courts interpreted Melendez-Diaz, and what can we expect from the courts in the near future? DAG Chamberlain will answer questions about this important subject.
A DISCUSSION OF OBJECTIVITY, SUBJECTIVITY AND BIAS IN FIREARM AND TOOLMARK IDENTIFICATION
Ronald Nichols, Bur. of Alcohol, Tobacco, Firearms, and Explosives
Firearm and toolmark identification as a discipline relies on experienced scientists and examiners to make determinations of common source which are primarily subjective in nature. In addition, because of the affiliation of most examiners, there have been claims that they can suffer from potential areas of bias which would in turn impact their primarily subjective conclusion with regard to common source. This presentation will discuss how objectivity, subjectivity and bias can influence conclusions that trained firearm and toolmark examiners offer. Despite published comments to the contrary, the comparative process has some objective elements associated with it and simply because such elements are not discreetly measured does not necessarily make them less objective. Even without the generation of numbers, the comparative process is an excellent technique by which objective observations with regard to pattern similarity and dissimilarity can be made and documented. Subjectivity enters the equation primarily when the examiner is ready to render a conclusion as to potential common source. In typical pattern matching, this is based generally on an individual examiner's baseline of what constitutes the best known non-match and whether or not the correspondence being observed exceeds that. Consecutive matching striations (CMS) is a means of describing agreement between two striated tool marks and then making an assessment of potential common source based on the amount of agreement one is seeing and comparing that to other published results. This issue of subjectivity is especially challenging because there is concern of bias entering the thought process of an examiner due to outside influences or because of his or her association with a law enforcement or prosecuting agency. Various concepts of bias will be discussed and explored. This will include a review of the available literature and a critical review of the studies that have been performed. This presentation will show how objectivity, subjectivity and bias are involved in firearm and toolmark identification. It will demonstrate that there is a large amount of objectivity in the comparative process. Furthermore, despite the subjectivity and potential bias, there are ways in which both can be minimized so as to help the examiner in providing the most accurate conclusions possible. These manners in which subjectivity and potential bias can be minimized will be discussed. Despite objections to the use of firearm and toolmark identification in the courts as a reliable scientific discipline because of a lack of objectivity along with too much subjectivity and bias, it can be used because the objections to its use in these areas are not well supported by either practice or the available literature. Indeed, the literature and good practice demonstrate that the discipline is based in scientific foundations and that the results of trained examiners can be considered reliable.
HOMEMADE EXPLOSIVES AND DEVICES
John Jermain, Bureau of Alcohol, Tobacco, Firearms and Explosives
Each year, the Bureau of Alcohol, Tobacco, Firearms and Explosives Forensic Science Laboratory in Walnut Creek receive hundreds of explosive exhibits submitted from throughout the Western United States. These exhibits range from commercial explosives and military ordnance to homemade explosive mixtures and improvised devices. Recipes to create explosives out of common household items are easily accessible online and people can post videos of their exploits on websites like YouTube. This presentation will focus on the manufacturing of homemade explosives and devices as well as demonstrating the explosive power these substances can produce.
TALKING FORENSICS WITH THE THIN MAN
Don Herron, The Dashiell Hammett Tour, author
Although author Dashiell Hammett, who wrote The Maltese Falcon, is known as the father of the hard-boiled American detective story, spotlighting tough guys, deadly dames and lots of gunplay, his earlier career as a Pinkerton's detective also gave him knowledge of forensic techniques which he drew upon in his fiction. From the scientific analysis used to wrap up the mystery of The Thin Man, to early methods of faking fingerprints and the effects of a .44 caliber gun at point blank range, Hammett dropped forensic science into his stories from the beginning. Don Herron has led the Dashiell Hammett Tour in San Francisco since 1977, and will discuss the intriguing role forensics played in Hammett's detective fiction. The thirtieth anniversary edition of his Dashiell Hammett Tour Book recently saw print, and among other titles he has written the biography Willeford on the life of cult crime writer Charles Willeford, author of Miami Blues.
NEXT GENERATION SOLUTIONS FOR CAPILLARY ELECTROPHORESIS & STR ASSAYS
This presentation will focus upon two next-generation solutions: The new 3500 Genetic Analyzer and the Identifiler Plus STR kit for challenged forensic samples. The gold standard for STR fragment analysis continues to be capillary electrophoresis (CE) genetic analysis platforms. The next generation 3500 (8 capillary) and the 3500xL (24 capillary) genetic analysis systems have improved upon the industry standard for CE by providing greater throughput, flexibility and ease of- use. We will discuss several advancements to this new CE system including: An improved polymer delivery pump design, ready-to-use consumables and containers, radio frequency identification (RFID) consumable tracking, improved user interface, quality control systems for rapid identification and re-injection of failed samples, increased throughput, improved power efficiency, peak height normalization, intuitive user software and integrated primary analysis software. Combining the improvements in next generation genetic analysis systems with STR assay improvements will enhance efficiency and performance across the human identification workflow. The presentation will also highlight the development of next generation STR assays which through the inclusion of new loci and improvements in amplification chemistry, deliver enhanced performance on the challenged and compromised samples most commonly encountered during casework investigations while still providing robust and reliable DNA profiles free of artifact peaks which may complicate interpretation. These developments further expand the range of samples from casework and missing persons investigations which can yield probative DNA results and are designed to meet the stringent requirements of the global forensic DNA community. Data demonstrating the effectiveness of the multiplexes will be presented including sensitivity, mixtures and models of inhibition and DNA degradation.