DNA Testimony Interpretation vs. Misinterpretation

1. DNA TestimonyInterpretation vs. Misinterpretation Michael J. Spence, Ph.D.

3. WHAT IS DNA? • DEOXYRIBONUCLEIC ACID • DNA is found in all nucleated cells • DNA is the genetic blueprint that encodes your physical appearance • Half of your DNA came from mom, the other half came from dad.

4. Blood Semen Hair Root Saliva Bone The most common sources of DNA: *All nucleated cells* Extraction

5. Clothing Rope, string, other bindings Guns, knives, and other weapons Brushes, combs Drink containers (saliva) Cigarette Butts & Chewing Gum (saliva) Toothbrushes (saliva) Stamps & envelopes (saliva) Earrings, rings, bracelets, other jewelry Steering wheels (sweat-skin cells) Contact DNA=epithelial/skin cells Countless Potential Sources of DNA Examined by Crime Labs

6. TWO MAJOR AREAS OF MISINTERPETATION DURING DNA TESTIMONY • TRANSFER EVENTS: DNA • DNA MIXTURE INTERPRETATION

7. Understanding secondary transfer, tertiary transfer-and subsequent DNA transfer events. • Modern-day DNA testing is fabulously sensitive and informative. However, DNA testing cannot tell us HOW DNA came to be in a specific location, …..nor can it tell us WHEN DNA came to be in that location. • If microscopic transfer events are so improbable, then how are cold & flu viruses so easily spread among our population? DNA Transfer Theory

8. The average human ‘sheds’ 40,000 skin cells per day. Are there ‘good shedders’, …. ‘medium shedders’, …. ‘poor shedders’? • With MICROGRAM quantities of DNA present in our blood, semen and saliva, …and millions of skin cells circulating through our ventilation systems, it is scientifically irresponsible to speculate, ….and conclude: • “Nanograms of his DNA were on it. Therefore, he must have touched it.” DNA Transfer Theory (cont.)

10. Who was Edmond Locard? • Professor Locard, Lyons University • Founded the world’s first forensic lab-1910 • ‘Sherlock Holmes of France’, trained Lyons Police Dept. crime scene investigators • Coined the phrase, “Every contact leaves a trace”, theorizing secondary, tertiary transfer, 43 years before Watson and Crick • ‘Theory’ became a time-tested universal PRINCIPAL of forensic investigations

11. CRIME SCENE VICTIM SUSPECT The Locard Exchange PrincipalWhat can transferred trace materials tell us about a crime scene? Vectors? Vectors? Vectors?

12. Nucleated Cells What can DNA tell usabout a crime scene? Determine the DNA profile Compare each crime scene DNA profile to profiles collected from suspects

13. How much DNA can you get from a little patch of nucleated cells? How much is 1 Gram? One packet of artificial sweetener How much is 1 mg? 1/1000 of a Gram How much is 1 mg? 1/1000 of a mg How much is 1 ng? 1/1000 of a mg or 1 Billionth of 1Gram How many cells to get 1 ng of DNA? Approximately 150 Compare each crime scene DNA profile to profiles collected from suspects Determine the DNA profile

14. Director of city police crime lab fired Database update reveals employees' DNA tainted evidence, throwing lab's reliability into question. http://truthinjustice.org/baltimorepdlab.htm By Julie Bykowicz and Justin Fenton, Sun reporters, August 20, 2008 Baltimore crime analysts have been contaminating evidence with their own DNA -- a revelation that led to the dismissal this week of the city Police Department's crime lab director and prompted questions Wednesday from defense attorneys and forensic experts about the professionalism of the state's biggest and busiest crime lab. Defense attorneys said any flaws in the city's handling of DNA could raise broader questions about evidence that is generally considered infallible. As testing becomes more sophisticated and new standards for labs emerge, cities across the country, including Houston and Seattle, have been discovering contamination issues that in some cases led to convictions being overturned.

16. CONTACT with items such as cell phones, door knobs/handles, pens, pencils, computer keyboards, TV remote controls, car keys, steering wheels, sunglasses, walkways, stairwells, railings, vending machines, etc. CONTACT with clothing/bedding/towels used by 1st person, handled by a 2nd person. Intimate contact such as kissing and/or sexual activity, hugs, handshakes, sharing cigarettes, sharing drink containers, etc. Transfer Events: DNA

17. Coughing, sneezing on an item, subsequently touched by a 2nd person. Saliva or blood from a 1st person deposited on a stairwell, walkway, or doorstep-subsequently tracked into a home by a 2nd person. The higher the moisture content (blood, sweat, tears, saliva) the more readily DNA will be transferred. What is meant by ‘initial DNA load’? Transfer Events: DNA, (cont.)

18. At the crime scene: Collection of SUBSTRATE CONTROLS Laboratory-based determination of the biological source: Is it blood, semen, saliva, or are we looking at an unknown source? If we have NO substrate controls (no information on ‘background DNA’) and NO tests for biological sources, how do we know the mechanism by which DNA arrived at the location it was found? WE DON’T! Proper Investigation ofDNA Transfer Events

19. DNA Testimony Misinterpretations to Avoid • The CARDINAL RULE: Do not speak outside of your expertise. • If you have no research experience on the issue, and you do not fully understand the results that HAVE been published, avoid phrases such as “The literature supports....” or “The literature does not support....” Do not speculate! • “Nanograms of his DNA were on it. Therefore, he must have touched it.” • Sometimes, “I don’t know.” can be the most intelligent response.

20. MISREPRESENTATION DURING DNA TESTIMONY DNA MIXTURE INTERPRETATION

21. Is this DNA a mixture? Major/Minor vs. Indistinguishable DNA Mixtures How many DNA contributors are present? Identifying obstacles to scientifically reliable DNA mixture interpretations. Calling the mixture. Statistical calculations. Characterizing DNA Mixures: Steps

22. This is not rocket science. If there are more than two alleles at ONLY one locus, we certainly might have a mixture of DNA. However, in order to be certain of a DNA mixture, more than two alleles should be noted at two or more loci. Otherwise, a SINGLE instance of a third allele could actually correspond to a rare individual who possesses a tri-allelic genotype at ONE locus. STEP 1-Is this a DNA mixture?

23. A Major/Minor DNA mixture should not be called unless a qualified Forensic Biologist has evaluated the electropherogram peak height landscape, ….and has arrived at a reliable scientific conclusion that a SINGLE SOURCE FULL DNA profile accounts for a majority of the DNA within the mixture. This conclusion often involves a KNOWN individual accounting for that major profile. Otherwise, the DNA mixture is composed of indistinguishable contributors. STEP 2-Is this a Major/Minor DNA mixture, or is it an Indistinguishable DNA Mixture?

24. If three alleles occur at two or more loci, the DNA mixture includes 2 or more people. If five or more alleles are observed at a locus, the DNA mixture includes 3 or more people. ….and so on, ….. STEP 3-How many contributors?

26. Simply too many contributors to the DNA mixture being evaluated. Indistinguishable minor contributors. Genetically-related contributors. Unknown DNA contributors. Calling allelic dropouts versus “This person’s DNA is simply not there!” STEP 4-Identifying obstacles

27. Person A can be excluded as a potential contributor to the DNA mixture on Item 1. Person B cannot be excluded as a potential contributor to the DNA mixture on Item 1. No scientifically reliable conclusion can be reached upon comparing Person C to the DNA mixture on Item 1. STEP 5-Calling the mixture

28. When the call is “Cannot be excluded”, the statement has no scientific or legal validity without a calculation establishing the STATISTICAL WEIGHT of the non-exclusion. Alleles occur within individuals from various ethnic populations at measurable percentages. The probability of inclusion (POI) can be calculated, using these known percentages. POI stats are used to establish statistical weight of a non-exclusion-using what is know as the Product Rule. STEP 6-Statistical calculations

29. “A DNA mixture of at least 3 individuals was observed, ….including a total of 58 alleles detected. Although there was no major profile, and we don’t know who the other DNA contributors might have been, the defendant could not be excluded. You see, ...only 5 of the his 24 alleles were missing from mixture. This allowed me to calculate the POI statistics without using the loci that showed allelic dropout. From this, I calculated that the lab would have to test somewhere between 5 million and 20 million randomly-selected individuals-depending on the ethnic population-before we would find an individual who cannot be excluded. And the defendant IS NOT excluded!”--------What is wrong with this picture? Faulty DNA Mixture Testimony

30. “A complex DNA mixture was observed on the firearm. No major profile was observed, and we do not have DNA standards providing clues as to the various weak contributors. Due to numerous allelic dropouts, the defendant was excluded. However, ….this conclusion does not take into account that the firearm may have been wiped down. Nor does it take into account that the item was discarded into an open area and exposed to countless months of weathering. Removal of DNA as a consequence of tampering, weathering, and degradation of DNA could account for the absence of the defendant’s DNA, which may have originally been on the item, …..but is now undetectable.” Again, what is wrong with this picture? More Faulty Testimony

32. Over a period of years, a Texas rancher fires numerous shots at the side of his barn. (the joke could center on a rancher from ANY state). The man paints a target on the barn, centering his paint job on a cluster of bullet holes that just happen to have landed in one area. The rancher gathers all of his friends-and claims ‘proof’ that he is a sharpshooter. How does this comical tale illustrate scientific misinterpretation of data?............................ Let’s answer that with an example: The Texas Sharpshooter Fallacy

33. Abraham Lincoln and John F. Kennedy were both presidents of the U.S., ….elected 100 years apart. Both Lincoln and JFK were shot by assassins with three-part names adding up to exactly 15 letters. Neither assassin made it to trial. Lincoln had a secretary named Kennedy, and Kennedy had a secretary named Lincoln. Both men were killed on a Friday while sitting next to their wives. Lincoln was at the Ford Theater, Kennedy in a Lincoln-manufactured by Ford. Example of the Texas Sharpshooter Fallacy:

34. Both Lincoln and Kennedy were succeeded by a vice-president named Johnson. Andrew Johnson was born in 1808 and Lyndon Johnson was born in 1908. Certainly, these facts prove some sort of cosmic connection between Abe and JFK, …..right? Perhaps we should look at ALL of the Abe/JFK facts, especially all of those ‘bullet holes’ that DO NOT line up, .....and were consequently ignored. For more on the Texas Sharpshooter Fallacy, go to: http://lpr.oxfordjournals.org/content/8/3/257.full.pdf?keytype=ref&ijkey=ehrDeU74Gi6ERv1 Example of the Texas Sharpshooter Fallacy (cont.)

35. Lawyer: Doctor, before you performed the autopsy, did you check for a pulse? Witness: No. Lawyer: Did you check for blood pressure? Witness: No. Lawyer: Did you check for breathing? Witness: No. Lawyer: So, then it is possible that the patient was alive when you began the autopsy? Real Life Testimony, I’m not making this up!

36. Witness: No. Lawyer: How can you be so sure, Doctor? Witness: Because his brain was sitting on my desk in a jar. Lawyer: But could the patient have still been alive nevertheless? Witness: Yes, it is possible that he could have been alive and practicing law somewhere. Real Life Testimony (cont.)

37. THE END