DNA and Serology
Modern DNA (deoxyribonucleic acid) testing technology has revolutionized forensic investigations and often plays an integral role in the investigations and prosecutions of military sexual assault offenses.
In many “he-said-she-said” sexual assault cases, DNA and serology can be the only hard evidence in the case, and understanding how to interpret, analyze, and implement this evidence properly at trial can often be the difference between an acquittal and a conviction.
In sexual assault cases that involve DNA, it is crucial to first understand what type of DNA and serology testing the forensic laboratory, typically the United States Army Criminal Investigative Laboratory (USACIL), conducted.
USACIL typically employs two different types of DNA testing, autosomal DNA testing and Y-STR testing. The two are as different as night and day and understanding the uniqueness of each variant of DNA testing, as well as serology testing, is absolutely critical to putting together a winning defense in the case.
If the defense attorneys do not understand DNA testing, it will be all but impossible for them present your story of innocence to the jury.
Y-STR DNA Testing
Y-STR DNA testing only detects male DNA by exclusively focusing on areas on the Y chromosome. It is most often seen in sexual assault cases where vaginal swabs are taken. In this scenario, the quantity of female DNA often “masks” the male DNA making autosomal STR testing impossible.
The ability of Y-STR DNA testing to focus directly on the male DNA allows the lab to detect and test even the slightest amount of male DNA that was present. Y-STR DNA testing was designed and is properly used, as a tool of exclusion, not of inclusion. It can be powerful evidence to show that an accused was not a match to a certain sample of DNA and to exonerate a suspect.
However, military law enforcement and prosecutors routinely utilize this form of testing to show that an accused’s DNA was a match or was consistent with the DNA sample in evidence. This is a misuse of the science.
Because the Y-STR testing focuses only on the Y-chromosome, as opposed to several chromosomes or markers, it is fundamentally less discriminating than autosomal DNA testing and generates statistical matching profiles that are typically closer to 1 in 300, rather than the 1 in a sextillion that autosomal DNA testing provides. In addition, because paternal lineage is passed down through the Y chromosome, a male individual will have the same DNA as his brother, father, grandfather, and the entire paternal line.
Serology is the testing of blood, semen, vaginal fluid, saliva, sweat, urine, and other bodily fluids. This form of testing is often done in conjunction with DNA testing and will be conducted based on the specific facts of the case.
Prior to actually testing a sample for DNA, the laboratory will often conduct what is known as an AP (acid phosphatase) and P30 test on the sample. These tests can provide a “presumptive positive” or “immunological indication” of semen but do not confirm that semen was present.
Often times, these presumptive tests will later be introduced into evidence at trial and a prosecutor will lead the jury to believe that an accused’s semen was present at a crime scene, or on the alleged victim, without any confirmatory testing.
In addition, in cases in which oral sex is an issue, USACIL often refuses to conduct Amylase testing, which can detect the presence of sweat or saliva. It is critical that you have a defense attorney who understands forensic evidence and knows how to utilize it during the initial investigation, during the pre-trial stages, and at the trial itself so that the forensic interpretation of evidence will not be improperly manipulated to convict you.
The USACIL DNA Report is not Enough.
In DNA cases, the government typically only provides the defense with the final USACIL report. Most military defense attorneys blindly rely on the final report and do not even realize that the report is simply a summary of typically hundreds of pages of data and forensic test results. The report itself is just the tip of the iceberg.
Forensic DNA and serology testing is technical, highly complex, and requires specialized skills to interpret. It is not clinical testing that provides a simple “positive” or “negative” result. When reviewing and interpreting DNA discovery, whether autosomal or YSTR, it is critical to answer at least these questions:
- Was the chain of custody intact?
- What lab standards and protocols were followed?
- What evidence was tested?
- Why was certain evidence not tested?
- Who tested the evidence?
- Was there any contamination during the testing process?
- What was the appearance and size of the samples and stains tested?
- What testing process techniques were used?
- What was the quantity of DNA obtained?
- What were the serology (Acid Phosphatase and P-30) results?
- Were immunological indications of semen found on the sample?
- Was spermatozoa found, and if so, in what quantity?
- Does the raw data support the conclusions in the report?
The only way to obtain this information is by filing a highly specific DNA discovery request and ensuring that a defense DNA expert is available to interpret the results and consult with the defense attorney on the case.
Problems with Forensic Laboratories
Prior investigation into quality of work and the accuracy of results at the nation’s largest criminal investigative laboratories have revealed significant problems with the qualifications of the analysts, the quality of the equipment, and the accuracy of the results.
These investigations have even uncovered cases where known fraudulent results were reported. Laboratories from New York City, Boston, Houston, West Virginia, and dozens more, including the famed FBI forensic testing laboratory, were exposed. Not to be left out, the U.S. Army Criminal Investigation Command (USACIL), responsible for nearly 200 lab employees, has also experienced problems with its testing.
Analysis of DNA results
A defense attorney must not only understand DNA and obtain all of the evidence, but they must also know how to analyze the results, incorporate them into the story of innocence, and present them to a jury. In conducting this analysis, the following threshold questions must be answered:
- If DNA is found, is it necessarily incriminating?
- Was the DNA found a “match” or deemed to be “consistent with” the accused’s DNA?
- If testing was conducted and no DNA was found, can this be utilized in the defense?
- If certain pieces of evidence were not tested, could they have contained exculpatory evidence?
The answers to these questions not only depend on the quality of the DNA laboratory testing, but are also specific to the facts of the case. That is, the results must be put into the context of the facts of the case. While it may appear difficult to overcome autosomal DNA evidence, all hope is not lost.
Although autosomal DNA testing is inherently more powerful and discriminating than Y-STR testing, many of the results produced are ambiguous at best. If the data shows that the DNA yielded a mixture of individuals and the results of that mixture were incomplete or inconclusive, it can be exposed that the accused was not an exact “match” to the DNA and other individuals’ profiles were present.
Put differently, the jury must understand the difference between DNA that is a weak association, is “consistent with,” or is an exact “match” to the DNA being analyzed. Similarly, in Y-STR DNA cases, a jury must understand that this is a testing of last resort and designed to exclude individuals, not to include them. Using Y-STR testing to include or “match” DNA is a fundamental misuse of the science. However, a jury may simply hear the term “DNA” and think the prosecutor has the proverbial smoking gun or magic bullet and be inclined to convict. It is therefore critical to understand the science and educate the jury.
Actual Acquittals in DNA Cases
At Bilecki & Tipon, we employ experts seasoned in the science of DNA. In addition to using the science for excluding and including parties in a case, DNA experts can scrutinize prosecution DNA reports to ensure the integrity of the process.
In one instance, what was presented by the prosecution as damning DNA evidence, turned out to be a type of DNA test that has only a fraction of the certainty of conventional tests. Moreover, our expert was able to identify flawed processing, which nullified the test results.
The bottom line? The government presented us with evidence from the DNA branch of USACIL, which purported that the DNA of our client was a “match” to that found on the underwear of the alleged victim. Mr. Bilecki worked alongside one of the nation’s leading DNA experts and discovered that the DNA “match” was, in fact, only a partial-profile match based on Y-STR DNA testing, as opposed to autosomal testing.
The result was, instead of the typical confidence rating of 1 in 36 sextillion, the confidence rating of the partial profile Y-STR DNA match in this case was actually around 1 in 500. Mr. Bilecki further discovered that several pieces of exculpatory evidence were never tested. At trial, Mr. Bilecki conducted a detailed cross-examination of the USACIL DNA examiner and revealed to the jury:
- The ratio of female to male DNA was too high to conduct autosomal DNA (the gold standard);
- The amount of DNA that was actually obtained was less than one half of one billionth of a gram;
- Not all of the markers on the Y chromosome that were analyzed were a match to the accused (thus the partial profile);
- The bedding, clothes, and other evidence collected was not tested for DNA, and;
- Y-STR DNA testing is designed to exclude a suspect, not to include a suspect.
Mr. Bilecki used the cross-examination to educate the jury on DNA and to present his client’s story of innocence. What began as a slam-dunk for the prosecution, turned out to be an air ball. Result: Not Guilty on all charges. This is just one example of how DNA cases that, on their face, look insurmountable, can be challenged and won at trial.
No strangers to tough DNA and serology cases, Bilecki & Tipon is ready to take and win even the most complex cases involving forensic evidence. If your case involves DNA, serology, or other complex forensic evidence, contact our office to discuss how we can tell your story of innocence. Call anytime, day or night, 24 hours a day, seven days a week. (808) 745-1041.