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DNA (Trace DNA)

Do you have case, usually a sexual assault case, where the prosecution says they have your DNA and it will convict you? Here are some thoughts for you and your military defense lawyer.

Many aspects of forensic science are based on Locard's Exchange Principle.

Locard speculated that every time you make contact with another person, place, or thing, it results in an exchange of physical materials. He believed that no matter where a criminal goes or what a criminal does, by coming into contact with things, a criminal can leave all sorts of evidence, including DNA, fingerprints, footprints, hair, skin cells, blood, bodily fluids, pieces of clothing, fibers and more. At the same time, they will also take something away from the scene with them.

In 1984, Sir Alec Jeffreys, a British geneticist, discovered the technique of DNA testing to determine a genetic “fingerprint” in a laboratory in the Department of Genetics at the University of Leicester, England. Jeffreys says he had a “eureka moment” in his lab after looking at the X-ray film image of a DNA experiment which unexpectedly showed both similarities and differences between the DNA of different members of his technician's family. Within about half an hour he realized the possible scope of DNA fingerprinting, which uses variations in the genetic code to identify individuals.

Couenhoven tells us that

DNA fingerprinting was first used in a police forensic test in 1986. Two teenagers had been raped and murdered in Narborough, Leicestershire, in 1983 and 1986 respectively. Although the attacks had occurred 3 years apart, similarities led the police to believe that one person was responsible for both. A suspect in custody, Richard Buckland, confessed to the most recent murder but not the earlier one. Jeffreys was asked to do DNA profiling on a blood specimen that was collected from the suspect and on tissue specimens and semen collected from the two victims.

This first use was successful use of DNA evidence was an exoneration case in which there was a false confession.

So, if you are accused of a sexual assault and they have your DNA on the SAFE Kit or clothing -- you and your military defense lawyer are going to have to discuss the defense of consent or that you had a honest and reasonable belief the person was consenting (otherwise mistake).

Some years ago I had a female client accused of drug use based on a urinalysis. The problem for the government was the sample showed male DNA in her--a female--sample.

Typically you and your military defense lawyer are going to see the DNA results in a report from USACIL. You will then have your DNA expert review the report and supporting document--the review looks for collection and testing errors. Absent any significant collection or testing errors it's difficult to challenge the evidence.

That said, there are times when the the government has what is called "trace DNA" and which is something you and your military defense counsel need to know about.

There are several overall principles to consider when you and your military defense lawyer discuss the relevance and value of DNA evidence in your court-martial. The presence of DNA is not always a binary choice as to guilt or innocence—the value of DNA evidence exists on a continuum.

  1. The relevance of DNA evidence is at its apogee when the suspect and a victim are strangers to each other and the suspect is a stranger to the scene of the crime. For example, a burglar breaks in to a home he has never been in before and sexually assaults a victim—the suspect's DNA is found at the home. The DNA evidence is highly relevant because that places him at the scene where he should never have been.
  2. DNA evidence's value and relevance is at its nadir when the “rape” suspect and the victim are known to each other, the suspect has regular access to the bed which is the alleged scene of the crime, the suspect and the victim have previously engaged in sexual activity on that bed or they have been in the same bed prior to the alleged assault. The likelihood of finding DNA in an alleged spousal sexual assault case are high. The DNA evidence is not relevant to corroborate or prove a sexual assault on a specific date and time.
  3. Another low-end situation is where an alleged rape is alleged to happen in your home and the complaining witness allegedly has trace DNA on her clothes. This is the central issue of trace DNA's value. If this is your home examiners can expect to find your DNA everywhere.
  4. The technical reliability and relevance of DNA evidence depends on many factors, including the quantity and quality of the sample analyzed, the reliability of the laboratory equipment or analysis technique; and the qualifications and skills of the examiner. Chap. 44, Essentially Yours: The Protection of Human Genetic Information in Australia (ALRC Report 96). Australian Law Reform Commission (30 May 2003) [https://www.alrc.gov.au/publications/report-96].

  5. Advances in DNA technology have brought problems and concerns. One such concern is the use of databases and statistics. More importantly for Appellant, a second concern is the presence or relevance of “touch DNA.” Touch DNA works well as evidence in cases at the apogee but not so when the facts are at the nadir. Epithelial or touch DNA evidence can be defined as evidence with no visible staining that would likely contain DNA resulting from the transfer of epithelial cells from the skin to an object. Can simply touching an object leave skin cells? It has been stated in publications that forensic scientists can obtain a DNA profile from as few as five to six cells. However, just because a surface is touched and a few skin cells are left behind does not guarantee a meaningful DNA profile can be obtained. Detecting and obtaining an interpretable DNA profile are two different concepts.
  6. Joe Minor, Touch DNA: From the Crime Scene to the Crime Laboratory. Forensics Magazine (December 2013) [https://www.forensicmag.com/ article/2013/04/touch-dna-crime-scene-crime-laboratory].

  7. Because extremely small samples of DNA can be used as evidence, greater attention to contamination issues is necessary when identifying, collecting, and preserving DNA evidence. DNA evidence can be contaminated when DNA from another source gets mixed with DNA relevant to the case. This can happen when someone sneezes or coughs over the evidence or touches his/her mouth, nose, or other part of the face and then touches the area that may contain the DNA to be tested. Because a new DNA technology called “PCR” replicates or copies DNA in the evidence sample, the introduction of contaminants or other unintended DNA to an evidence sample can be problematic.
  8. What Every Law Enforcement Office Should Know about DNA Evidence, National Commission on the Future of DN Evidence, National Institute of Justice.

  9. Since 1997, when researchers first showed that it was possible to gather genetic information about a person based on skin cells they had left on an object, this type of trace evidence, also known as touch DNA, has been increasingly collected from surfaces such as door and gun handles. Until recently, this type of DNA has been regarded as incontrovertible proof of direct contact. But a growing number of studies show that DNA does not always stay put. For example, a person who merely carried a cloth that had been wiped across someone else's neck could then transfer that person's DNA onto an object he or she never touched, according to a study published earlier this year in the International Journal of Legal Medicine. Similarly, Cynthia M. Cale, a master's candidate in human biology at the University of Indianapolis, recently reported in the Journal of Forensic Sciences that a person who uses a steak knife after shaking hands with another person transfers that person's DNA onto the handle. In fact, in a fifth of the samples she collected, the person identified as the main contributor of DNA never touched the knife. Cale and her colleagues are among several groups now working to establish how easily and how quickly cells can be transferred—and how long they persist. “What we get is what we get,” Cale says, “but it's how that profile is used and presented that we need to be cautious about.”
  10. Peter Andrey Smith, When DNA Implicates the Innocent. Scientific American, 1 June 2016. [ ]

  11. Secondary transfer of human DNA through intermediary contact is far more common than previously thought, a finding that could have serious repercussions for medical science and the criminal justice system, report investigators. Increasingly important to criminal investigations, DNA analysis once required substantial samples of blood or other bodily fluids but advances in the field now make it possible to produce a complete genetic profile of a suspect from just a few cells left behind -- so-called "touch DNA." The emerging concern, long considered a theoretical risk but only now systematically confirmed by the UIndy study, is that the presence of those cells does not prove that the person actually visited the scene or directly touched the object in question. The DNA easily could have been transferred by other means.
  12. University of Indianapolis. "Study raises questions about DNA evidence." ScienceDaily. ScienceDaily, 28 October 2015. [ ]

  13. Low-quantity or -quality samples further raise concerns related to inadvertent transfer or contamination of DNA. Again, in the early days of forensic testing, analysts required a large quantity of biological material to conduct a DNA analysis. In such cases, it was unlikely that the blood spot or semen stain ended up at the scene by chance. But as sample sizes have dwindled to a mere handful of cells and testing of skin cells routinely shed throughout the day becomes more common, transfer and contamination have become increasingly vexing concerns. Murphy (2015) compiled a list of some of the most prominent studies of inadvertent transfer, which show that DNA is routinely found even when the depositor did not come into direct contact with that person or place. Traces of DNA can transfer through laundry, through proximity to sneezes or speech, or even, in one high-profile case, through medical equipment. DNA also shows remarkable persistence; it can endure for a long period of time, even on surfaces that have been cleaned. The ease with which small quantities of DNA can end up in unexpected locations underscores the need for rigorous cleaning and anti-contamination practices.

DNA also shows remarkable persistence; it can endure for a long period of time, even on surfaces that have been cleaned. The ease with which small quantities of DNA can end up in unexpected locations underscores the need for rigorous cleaning and anti contamination practices. Unfortunately, as extensively cataloged (Faigman et al. 2016, 2017; NRC 2009), the history of crime-scene laboratories embroiled in scandals related to incompetence or poor management gives cause for concern that such meticulousness may not be uniformly observed in the testing environment.

Erin Murphy, Forensic DNA Typing. 1 ANNU. REV. CRIMINOL. 497-515 (2018). [ ]

  1. While the prosecution worries about the “CSI effect” in cases where they have no forensic evidence, the defense worries about the CSI effect when there is forensic evidence because a jury assumes the infallibility of the forensic science. The “infallibility” of DNA as evidence is a myth because, "It's not really a case of who the DNA could have come from; it's more a question of how it got there." Research done at the University of Indianapolis in Indiana has highlighted how unreliable touch DNA evidence can be. “We have found that it is relatively straightforward for an innocent person's DNA to be inadvertently transferred to surfaces that he or she has never come into contact with. This could place people at crime scenes that they had never visited or link them to weapons they had never handled. Such transfer could also dilute the statistics generated from DNA evidence, and thereby render strong genetic evidence almost insignificant.” C. M. Cale et al. J. Forensic Sci. http://doi.org/8j2; 2015; Cynthia M. Cale, Forensic DNA evidence is not infallible. 526 NATURE 611 (Oct. 2015).
  2. You and your military lawyer should consider the difference between “primary transfer” DNA and “secondary transfer” (touch) DNA, When asked to determine whether or not the DNA he was testing resulted from a “primary” transfer or a “secondary” transfer he should honestly admitted that he was not able to make such a determination.
  3. Perhaps as I had in a recent case, the government’s DNA expert testifies that DNA from skin cells – the possible source of the DNA he analyzed in the case were like “chalk on a chalk board. And, like chalk on a chalkboard, if one touches that chalk and then touches another object some of the DNA picked up would be transferred to the other object. The “infallibility” of DNA as evidence is a myth because, "It's not really a case of who the DNA could have come from; it's more a question of how it got where it was found. Cynthia M. Cale, Forensic DNA evidence is not infallible. 526 NATURE 611 (Oct. 2015).

I have many other references on the topic as does my go-to DNA expert which further support the points above and present concerns you and your military defense lawyer should be aware of, consider, prepare for, and present.

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