Laboratory documentation of “sloppy work” should be encouraged. It should be scrutinized inside and outside of the laboratory. Within the laboratory, it can be a path to improvements. Outside the laboratory world, reporting on problems, quotidian and catastrophic alike, can increase the level of public and professional understanding of how forensic science is practiced. However, it is important to be clear about the nature, severity, and implications of specific “mistakes,” “errors,” and “contamination.” These terms cover a variety of phenomena.
Even before the earliest days of PCR-based DNA typing, it has been known that “contamination” is an omnipresent possibility. It can result from extraneous DNA in materials from companies that supply reagents and equipment, from the introduction of the analyst’s DNA into the sample being analyzed (“for example, when the analyst talks while handling a sample, leaving an invisible deposit of saliva” [2]), from inadequate precautions against transferring DNA from one test with one sample over to another test with a different sample (a form of “cross-contamination”), and so on. Many forms of contamination are detectable, but they can complicate or interfere with the interpretation of an STR profile [3]. Cross-contamination of a crime-scene sample with a potential suspect’s DNA either before or after it reaches the laboratory is particularly serious because it could result in a false match.
As described in an appendix below, it appears that only one of the 23 cases (#22) involved a false report of a match, and the report was corrected before any charges were filed. However, Bill Thompson presented a different case as a premier example of "false cold hits" [4, p. 230]. In his latest publication on errors in DNA typing, he wrote that
[W]hile the Washington State Crime Patrol Laboratory a cold-case investigation of a long-unsolved rape, it found a DNA match to a reference sample in an offender database, but it was a sample from a juvenile offender who would have been a toddler at the time the rape occurred. This prompted an internal investigation at the laboratory that concluded that DNA from the offender's sample, which had been used in the laboratory for training purposes, had accidentally contaminated samples from the rape case, producing a false match. [4, p. 230].Thompson noted that he "assisted the newspaper in the investigation" [4, p. 341 n.12]. Apparently, he was referring to case #5 in the article (although the article labels it a homicide case). In any event, it is the only case Thompson lists as an example of a false match in Washington.
My conclusion is that the Washington cases certainly establish that mistakes of many types can occur in DNA laboratories and that some types of mistakes can produce false matches, false accusations, and even false convictions. But none of the 23 are themselves instances of false charges or false convictions. This conclusion neither condones the mistakes nor excludes the possibility that DNA has produced such outcomes in Washington. But it may help put the 23 cases and the writing about them in perspective.
References
- Sheldon Krimsky & Tania Simoncelli, Genetic Justice: DNA Data Banks, Criminal Investigations, and Civil Liberties (2011)
- DNA Testing Mistakes at the State Patrol Crime Labs, Seattle Post-Intelligencer, July 21, 2004, 10:00 pm, http://www.seattlepi.com/local/article/DNA-testing-mistakes-at-the-State-Patrol-crime-1149846.php
- Terri Sundquist & Joseph Bessetti, Identifying and Preventing DNA Contamination in a DNA-Typing Laboratory, Profiles in DNA, Sept. 2005, at 11-13, http://www.promega.com/~/media/Files/Resources/Profiles%20In%20DNA/802/Identifying%20and%20Preventing%20DNA%20Contamination%20in%20a%20DNA%20Typing%20Laboratory.ashx
- William C. Thompson, The Myth of Infallibility, in Genetic Explanantions: Sense and Nonsense 227 (Sheldon Krimsky & Jeremy Gruber eds. 2013)
Related postings
- "Genetic Justice": The Potential and the Real, June 6, 2011
- There But For the Grace of God ... The “horrific false-positive DNA match”, May 27, 2011
- Have DNA Databases Produced False Convictions?, July 7, 2012
- "Human Error, Bias, and Malfeasance" in DNA Databases and Law Reviews, Dec. 22, 2012
- Good Point, Bad Math: DNA Database Statistics Misunderstood (Again), July 26, 2013
- Error on Error: Quashing Brian Kelly's Conviction, Dec. 7, 2013
APPENDIX
23 and Me
This Appendix quotes the newspaper descriptions in full, then offers my own remarks.
23 and Me
This Appendix quotes the newspaper descriptions in full, then offers my own remarks.
EXAMPLE NO. 1
Problem: Cross-contamination
When and where: July 2002, Spokane lab
Forensic scientist: Lisa Turpen
Case: child rape
What happened: Turpen contaminated one of four vaginal swabs with semen from a positive control sample. Corrected report issued almost two years later in March 2004. ....Yakima prosecutors offered plea deal during the trial, with defendant pleading guilty to two gross misdemeanors. Turpen's mistake was a factor, according to defense.”
REMARKS: I do not know what “semen from a positive control sample” means. When DNA from a cell line is used to ensure that PCR is amplifying those alleles, the cell-line DNA is known as a positive control sample. This example does not sound like a case of contamination involving that kind of a positive control. Adding semen to a vaginal swab obviously is unacceptable, but if the other three swabs produced a single male DNA profile and the fourth showed two male profiles in a case involving a single rapist, the anomalous profile would not be falsely matched to anyone.
EXAMPLE NO. 2
Problem: Erroneous lab report
When and where: August 2002, Seattle lab
Forensic scientist: William Stubbs
Case: Fatal police shooting of Robert Thomas
What happened: Two hours before testifying at inquest, Stubbs discovered his crime lab report was wrong and notified prosecutor. His report said test found brown stain on gun was likely blood, but his notes had no indication of blood. ... Corrected report issued in September 2002. ... Co-worker reviewing case did not catch mistake.
REMARK: Does not involve DNA typing.
EXAMPLE NO. 3
Problem: Self-contamination
When and where: April 2001, Spokane lab
Forensic scientists: Charles Solomon, Lisa Turpen
Case: rape/kidnapping/assault
What happened: In separate tests, Solomon and Turpen contaminated hair-root tests with their own DNA. Solomon also contaminated reference blood sample with his DNA. ...Three defendants were convicted.
REMARK: There is no suggestion of a false match here.
EXAMPLE NO. 4
Problem: Testing error
When and where: September 2002, Marysville lab
Forensic scientist: Mike Croteau
Case: robbery/assault
What happened: Rushing to meet deadlines, Croteau mixed up reference samples from victim and suspect. He reported incorrect findings verbally to prosecutor, then discovered his mistake. ... Defendant pleaded guilty.
REMARK: What is the mistake here? It must be something more than using the wrong names for the two samples that were compared to produce a false match.
EXAMPLE NO. 5
Problem: Cross-contamination
When and where: August 2003, Seattle lab
Forensic scientist: Robin Bussoletti
Case: homicide
What happened: Bussoletti likely contaminated work surface while testing a blood sample from a convicted felon during training. Next DNA analyst who used work station noticed contamination in chemical solution that is not supposed to contain DNA.
REMARKS: Definitely sloppy -- and potentially falsely incriminating if work surface was then used without a thorough cleaning for casework.
EXAMPLE NO. 6
Problem: Cross-contamination
When and where: January 2004, Tacoma lab
Forensic scientist: Jeremy Sanderson
Case: child rape
What happened: Sanderson failed to change gloves between handling evidence in two cases. He noticed contamination in chemical solution. ... Defendant convicted and sent to prison.
REMARK: Is this a case of cross-contamination of samples?
EXAMPLE NO. 7
Problem: Error during testing
When and where: June 2002, Seattle lab
Forensic scientist: Denise Olson
Case: aggravated murder
What happened: Olson did initial test to look for blood on shoes. She got weak positive result, then threw out swabs. She didn't document findings or notify police. Kirkland police complained because discarded swabs couldn't be tested for DNA. ... Shoes sent to private lab for retesting. ... Defendant Kim Mason convicted and sentenced to life without release.
REMARK: Not a false match
EXAMPLE NO. 8
Problem: Error in DNA test interpretation
When and where: October 1998, Seattle lab
Forensic scientist: George Chan
Case: rape
What happened: Chan misstated statistical likelihood of match with suspect. Co-worker reviewing case didn't catch error. ... Pierce County prosecutor noticed mistake at pretrial conference in September 2000. ... Defendant convicted.
REMARK: Not a false match
EXAMPLE NO. 9
Problem: Error in testing procedure
When and where: September 2002, Seattle lab
Forensic scientist: Denise Olson
Case: robbery/assault
What happened: Olson tested known DNA samples before evidence collected at crime scene -- a violation of lab procedure aimed at preventing cross-contamination. A co-worker caught the mistake while reviewing the case.... Tests were redone. ... Defendant pleaded guilty.
REMARK: This departure from protocol raises the risk of an incriminating case of cross-contamination, but there is no indication that any cross-contamination occurred.
EXAMPLE NO. 10
Problem: Self-contamination
When and where: November 2002, Tacoma lab
Forensic scientist: Mike Dornan
Case: rape
What happened: Dornan contaminated DNA test of victim's underwear with his own DNA. May have resulted from talking during testing process.... Defendant pleaded guilty.
REMARK: No false match.
EXAMPLE NO. 11
Problem: Unknown source of contamination
When and where: January 2004, Tacoma lab
Forensic scientist: Christopher Sewell
Case: homicide
What happened: Sewell found low level of DNA from unknown source in blood sample from victim. May have come from blood transfusion of victim before death. ... Case pending.
REMARK: The “unknown source of contamination” does not seem to have produced a false match if peak heights indicated a minor contributor, and the major contributor was the defendant,
EXAMPLE NO. 12
Problem: Self-contamination
When and where: March 2004, Tacoma lab
Forensic scientist: William Dean
Case: rape
What happened: Dean contaminated control sample with his own DNA while testing police evidence. ... No suspect.
REMARK: No suspect, no contamination of a crime-scene or suspect sample, no false match.
EXAMPLE NO. 13
Problem: Unknown source of contamination
When and where: January 2003, Spokane lab
Forensic scientist: Lisa Turpen
Case: murder
What happened: Turpen found unidentified female DNA in control sample while testing evidence in Stevens County double-murder case.... Defendant convicted.
REMARK: No contamination of a crime-scene or suspect sample, no false match.
EXAMPLE NO. 14
Problem: Unknown source of contamination
When and where: January 2003, Spokane lab
Forensic scientist: Lisa Turpen
Case: robbery/kidnapping
What happened: Turpen found unidentified female DNA in control sample while testing evidence in Yakima County case. Evidence tested same day as evidence in Example No.13.... Case pending.
REMARK: No contamination of a crime-scene or suspect sample, no false match.
EXAMPLE NO. 15
Problem: Self-contamination
When and where: September 2003, Marysville lab
Forensic scientist: Greg Frank
Case: murder
What happened: Frank contaminated control samples with his own DNA during testing in Snohomish County case. ...Case pending.
REMARK: No contamination of a crime-scene or suspect sample, no false match.
EXAMPLE NO. 16
Problem: Self-contamination
When and where: September 2003, Marysville lab
Forensic scientist: Greg Frank
Case: child molestation/rape
What happened: Frank contaminated control samples with his own DNA during testing in Kitsap County case. ... Defendant pleaded guilty.
REMARK: No contamination of a crime-scene or suspect sample, no false match.
EXAMPLES NO. 17 & 18
Problem: Unknown source of contamination
When and where: October 2003, Seattle lab
Forensic scientists: Phil Hodge, Amy Jagman
Cases: unknown
What happened: Hodge and Jagman both discovered unknown source of contamination in chemical used during DNA testing. Chemical discarded and evidence retested.
REMARK: No contamination of a crime-scene or suspect sample, no false match.
EXAMPLE NO. 19
Problem: Self-contamination
When and where: October 2002, Spokane lab
Forensic scientists: Charles Solomon, Lisa Turpen
Case: murder
What happened: Solomon found Turpen's DNA on three bullet casings retrieved from scene of Richland double murder. ... Defense expert disputed this at trial, testifying that DNA profile belonged to unknown female. ... Defendant Keith Hilton convicted.
REMARK: No false match.
EXAMPLE NO. 20
Problem: Cross-contamination
When and where: February 2002, Tacoma
Forensic scientist: Mike Dornan
Case: child rape
What happened: Dornan contaminated evidence in King County rape case with DNA from a previous case, likely by failing to properly sterilize scissors. ... Defendant pleaded guilty to a reduced charge before contamination was discovered.
REMARK: I presume that if the previous case were the defendant’s and that is what led to the charge against the defendant, the newspaper would have so stated. That would have been a false match.
EXAMPLE NO. 21
Problem: Self-contamination
When and where: January 2001, Marysville lab
Forensic scientist: Brian Smelser
Case: rape
What happened: Smelser contaminated three tests with his own DNA in Kirkland rape case. Prosecutor had to send remaining half-sample to California lab for retesting.... Defendant pleaded guilty to reduced charge.
REMARK: No false match.
EXAMPLE NO. 22
Problem: Error in testing
When and where: December 2002, Seattle lab
Forensic scientist: Denise Olson
Case: rape/attempted murder
What happened: Olson misinterpreted DNA results, telling Seattle police their suspect was a match. Co-worker caught error 11 days later, just as charges were about to be filed.... Case unsolved.
REMARK: A false positive report (not resulting from contamination).
EXAMPLE NO. 23
Problem: Self-contamination
When and where: January 2004, Seattle lab
Forensic scientist: George Chan/William Stubbs
Case: child rape
What happened: Chan's DNA found in suspect's boxer shorts by Stubbs. Problem traced to Chan talking to Stubbs during testing.... Suspect pleaded guilty.
REMARK: No contamination of a crime-scene or suspect sample, no false match.
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