Category Archives: DNA

Greg Taylor and Darryl Hunt programs on April 12, 2012

Two programs featuring NC exonerees Greg Taylor and Darryl Hunt will be broadcast on April 12, 2012.

The WRAL documentary, “6,149 Days” which premieres on April 12 at 8:00 pm recounts the flawed investigation that led to Greg Taylor’s conviction, Taylor’s 6,149 days in prison, and the fight to set him free. Steven D. Hammel, Vice President and General Manager of WRAL-TV said in a statement, “It is the mission of our dedicated documentary unit to tackle in-depth topics and social issues. Greg Taylor’s story exposes serious flaws in our state’s criminal justice system. It is our hope that this program can be a force for positive change.”

The documentary will be broadcast commercial-free on WRAL-TV in Raleigh, WJZY-TV in Charlotte and WILM-TV in Wilmington and will be followed by a half-hour live discussion with retired police chief Darrel Stephens of Charlotte and state representative Rick Glazier of Fayetteville. Additional information including court documents, photos, and a trailer can be viewed here.

Darryl Hunt’s case will be featured on Investigation Discovery series “Cold Blood” at 9 p.m. on April 12. The episode will include interviews with Darryl Hunt who was twice convicted for the murder of Deborah Sykes based on faulty eyewitness identification evidence. Hunt served 18.5 years for a crime he did not commit and was exonerated ten years after being excluded as a suspect by DNA evidence. Also interviewed in the program are: Howard Cross, Sykes’ friend; Sgt. Chuck Byrom, Winston-Salem police; Mark Rabil, attorney and Winston-Salem resident; Phoebe Zerwick, Winston-Salem Journal (1987-2008); and Regina Lane, rape victim. To check local listings, click here.

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DNA Mixture Analysis – Is It Subjective or Objective?

DNA is often regarded as the gold standard of forensic science because of its purported objectivity, which makes it immune to subjectivity and bias. The National Academy of Sciences 2009 Report, Strengthening Forensic Science in the United States: A Path Forward even concluded that “[w]ith the exception of nuclear DNA analysis, . . . no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source.” (See p. 7.)

If it were truly objective, contextual information would not affect DNA analysis. In reality, however, when human examiners analyze complex DNA mixtures, the interpretations may be based on subjective judgments and may be influenced by contextual information to fit existing beliefs and expectations.

A recent study by Itiel E. Dror and Greg Hampikian, published in the journal Science and Justice, examined the effect of contextual information on DNA mixture interpretation. The study involved a DNA mixture analysis from a gang rape case in Georgia, where the case analyst had received contextual case information. The researchers then presented the same DNA evidence, without the contextual information, to seventeen independent DNA expert analysts.

In the actual case, one assailant agreed to testify against the other suspects in return for a lighter sentence. According to the Georgia rules of evidence, however, the assailant’s testimony was admissible only if the prosecution offered corroborating evidence. Only the DNA evidence provided the needed corroborating evidence. In the case, the analysts determined that the suspects—including Suspect 3, the primary suspect—could not be excluded from being contributors to the mixture. The analysts knew that without this determination, the informant’s testimony would have been disallowed.

When the researchers presented the original DNA evidence to seventeen independent analysts without the contextual information, with respect to Suspect 3, the independent analysts reached varied results: one concluded that Suspect 3 could not be excluded; four found the analysis inconclusive; and twelve excluded Suspect 3.

This result indicates that subjectivity may be present in purportedly objective DNA mixture analysis. Further, the varied conclusions by the analysts indicate that consistent and reproducible analysis of complex DNA mixtures may not always be possible.

Other DNA interpretation studies have been conducted of several laboratories by Dr. John M. Butler of the NIST laboratories. His studies raise similar issues, including questions about the differing statistical results produced by labs analyzing the same DNA mixture.

The Scientific Working Group on DNA Analysis Methods (known as SWGDAM) acknowledged in their publication (Interpretation Guidelines for Autosomal STR Typing by Forensic DNA Testing Laboratories, 2010) that “[d]ue to the multiplicity of forensic sample types and the potential complexity of DNA typing results, it is impractical and infeasible to cover every aspect of DNA interpretation by a preset rule,” thereby keeping the door open for subjective interpretation by the DNA analyst. This door is also open for knowledgeable experts to challenge interpretation of that data, particularly when it comes to the most difficult DNA samples to interpret, Low Copy Number (LCN) mixtures.

Anand Patel, UNC Law Student and NC State University Ph.D. Candidate contributed to this post.

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Update to “Freedom on the line for two North Carolina men”

A three-judge panel in Asheville ruled today that Kenneth Kagonyera and Robert Wilcoxson are innocent. The men who spent ten years in prison were exonerated by the judges’ ruling. This case which involved DNA testing that pointed to another suspect is the third case that has been heard by the N.C. Innocence Inquiry Commission and the second to result in an exoneration.

See the Asheville Citizen-Times for additional coverage.

Read previous post here.

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Warning about SBI DNA Reports

By Mark Rabil

Have you been given a report from the SBI Lab (now the State Crime Lab) that says the results of DNA testing are “inconclusive”?  Well, you should not necessarily believe it. The Tamera Bean noncapital murder case that was tried in Asheboro this month is a case in point. Defense Attorney David Botchin did a great job of doggedly pursuing the records in that case. This was a self-defense case in which the State contended the female defendant shot her boyfriend and staged the crime scene. In discovery, the SBI gave the DA and the DA gave the defense a report that said DNA testing on one of the shells was “inconclusive.” That was flat wrong: the defendant was excluded and the decedent was likely included. Read on to see why you cannot take the word of these lab reports.

It turns out three reports were written about the same SBI DNA testing in this case: the first report in 5/09 said defendant excluded as source of DNA; the second report in 6/09 changed the conclusion and said the results were “inconclusive” (the internal SBI lab “reviewer” made the analyst change the report, improperly); and the third report in 8/11 said defendant excluded. In the third report that was ordered by the court, the lab also added some language about how the sample was insufficient to submit to CODIS, a fact not in the first report, and intended to help the prosecution minimize the effect of the new report.

The State Crime Lab interpretation guidelines have gone through many revisions in recent years regarding the interpretation of mixtures and the reporting of inconclusives. (For the Crime Lab’s Interpretation Guidelines, you can visit the NCDOJ website or the NCIDS website or contact Sarah Rackley for assistance in locating the relevant procedures.) Counsel must remain alert to reporting language, however. According to the Ombudsman’s Report, the Crime Lab policy is that testimony should be based on the standards in effect when the testing was conducted, not the current standards (see p. 25). From the Bean case it isn’t clear whether analysts will identify whether the report was prepared according to the old protocols or the new ones. We also don’t know how many times a false inconclusive has gone misreported and undetected in other DNA cases or whether it is still happening in current cases. If you are working on a case where you think a false inconclusive may have been reported, contact IDS’s Forensic Resource Counsel (

Editor’s note:

Click here to read Mark Rabil’s August 29 guest column on the Bean case in the Winston-Salem Journal, as well as Judge Joseph John’s response and David Botchin’s response to the column.

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Freedom on the line for two North Carolina men

By Charlotte Stewart, UNC Law Student

This week a three-judge panel, formed as part of the N.C. Innocence Inquiry Commission process, is hearing a case which could exonerate two North Carolina men of murder convictions.

Kenneth Kagonyera and Robert Wilcoxson were convicted of the murder of Walter Rodney Bowman in 2000 in Buncombe County. Last Tuesday, however, a DNA analyst gave testimony regarding evidence found near the crime scene indicating that Kagonyera and Wilcoxson may not have been involved in the crime.

The DNA was found in saliva samples taken from bandanas that may have been used in the robbery that led to Bowman’s murder. The DNA did not match that of any of the six men originally investigated for the crime, but it did match that of another man, currently in prison, who was not originally charged with the crime.

In 2003, inmate Bradford Sumney was implicated by another prisoner in Bowman’s slaying and in 2007, there was a hit in the state’s CODIS database showing a match between the DNA sample from the bandanas and Sumney’s DNA. The DNA analyst who discovered the match testified that he sent notice to the Sheriff’s Office and the District Attorney’s Office that a match had been made to someone other than the two men convicted of the crime. However, according to the Innocence Commission investigation, no action was taken.

Kagonyera and Wilcoxson, currently represented by attorneys Noell Tin and Chris Fialko of Charlotte, initially maintained their innocence, but later pleaded guilty to the crime to avoid the death penalty.

It may take over a week for the panel to hear all of the relevant testimony, after which the judges will vote on whether to overturn the convictions, which requires a unanimous vote among the three judges.

The N.C. Innocence Inquiry Commission was formed in 2006 to investigate cases that may have ended in wrongful convictions and is the first of its kind in the country.

To follow continuing coverage of the hearing in the Asheville Citizen-Times, click here.

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CODIS: Combined DNA Index System

By Sarah Rackley
Edited by Dr. Maher Noureddine, forensic DNA expert

Note: Where State Crime Lab policies and procedures are referenced, I have cited to the most recent version that I have access to.

What it is:
CODIS (Combined DNA Index System) is the FBI’s program that allows forensic DNA laboratories to create and search databases of DNA profiles. The federal DNA Identification Act of 1994 authorized the FBI to create CODIS and set national standards for forensic DNA testing. CODIS became fully operational in 1998. CODIS databases exist at the local (LDIS), state (SDIS), and national levels (NDIS). This tiered architecture allows crime laboratories to control their own data, enabling each laboratory to decide which profiles it will share with the rest of the country (Source:,

How it is used:
CODIS contains an index of convicted offender and arrestee profiles. These profiles are developed from biological samples submitted when an individual is arrested for or convicted of statutorily specified crimes. (See Crime Lab procedures for CODIS and DNA Database Procedures.) Each state has different qualifying offenses, and there are requirements for entering the profiles into the local, state, or national database. (See G.S. 15A-266)

When biological evidence is collected from a crime scene or victim, a DNA profile of a suspect may be developed. This “forensic unknown profile” can be compared to profiles in the convicted offender and arrestee index. Regular searches are conducted of all DNA profiles in the National DNA Index System (NDIS) and resulting profile matches are automatically returned to laboratories that submitted them.

If there is a computer-identified “match” or “offender hit,” the Crime Lab initiates procedures to obtain a new DNA sample from the suspect and perform  DNA analysis in the lab to confirm the match. If you have a case where a CODIS hit was made, it is important to read Section 6 of the Crime Lab Procedures to ensure that the correct reviews and analysis has occurred.

Considerations if you have a CODIS cold hit case:

  • Is there a direct or reasonable correlation between the forensic sample that was collected from the scene and the crime itself? What are the chances that the sample belongs to a bystander, unrelated to the crime? This is especially important if the sample was developed as a “Touch DNA” sample. Using new technologies, minute amounts of genetic material can now be used to generate a profile that is suitable for CODIS.
  • How was the “forensic unknown profile” from the crime scene entered into CODIS? Consider possible sample mix up, contamination, and interpretation problems that could have occurred when the sample was entered. Who was the analyst who entered the sample? Some of the analysts who entered samples in the early 2000s are no longer employed by the State Crime Lab or were cited in the Swecker report, which raised concerns about the reliability of Crime Lab work.
  • How and why was the DNA sample collected from your client? Are there grounds to challenge that collection? If your client’s sample was in the database from a collection in NC, was the qualifying conviction or arrest pursuant to G.S. 15A-266.3?
  • Have you received the lab report from the Crime Lab’s analysis of the database “match?”
  • Finally, consider the standard questions you would ask regarding DNA analysis: How many loci match? What is the statistical significance of the “match”? (See this LA Times article.) How was that statistical significance calculated? (See this research on the probability of an erroneous attribution in “cold hit” cases) How did cognitive bias affect the analysis?

Motions practice:
A great resource for motions you may consider filing in CODIS cold hit cases is PocketExpert Consulting, LLC. This website has sample motions including the following challenges: when DNA has been taken from a client who has not committed a qualifying offense, the taking of DNA from a parolee, the statistical significance of the purported “cold hit,” the unreliability of a 9+ loci match, and CODIS vulnerabilities.

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Touch DNA

Posted by Sarah Rackley
Edited by Dr. Maher Noureddine, forensic DNA expert

The SBI lab started analyzing “touch DNA” around 2006. Now that the lab is capable of analyzing this type of evidence, investigators are collecting it more often, and I am hearing about it coming up in more cases.

So, what is touch DNA and what does it mean for your case? Touch DNA refers to the DNA that is left behind from skin cells when a person touches or comes into contact with an item. Trace DNA would be a more accurate way to characterize this evidence, as small amounts of DNA can be left behind simply from the shedding that our bodies do naturally. An average size human will shed thousands of skin cells every minute, and each cell will contain a full copy of that individual’s genome. Small amounts of DNA can also be left behind from a cough or a sneeze.

So, when the SBI lab or investigators refer to “touch DNA,” you should think – very small amounts of DNA. With “touch DNA,” physical contact is sometimes assumed or hypothesized. Therefore, you should also think about the physical environment from which this evidence was collected. Always consider alternative explanations for why someone’s DNA would be expected to be found in a given area or on a given surface.

Because such a small amount of evidence is being analyzed (as few as 5-10 cells) contamination and transfer of DNA are issues that should be considered through each step in the analysis. Evidence collection, extraction of DNA, amplification and interpretation are four areas where attorneys should be aware of possible problems.

Evidence collection:
Trace DNA can be collected either in the field by law enforcement officers or crime scene investigators, or it can be collected from a piece of evidence (such as a gun) at the crime lab. Attorneys should ask:

  • What is the collection technique?
  • The use of evidence collection devices on multiple samples (such as fingerprint brushes) can be a source of contamination. How was this limited?
  • What type of tape or swab is used? Wet or dry swab? How many times was the piece of evidence swabbed?
  • Are swabs from different areas kept separate? (i.e., the swab from trigger kept separate from swab from other parts of gun)

Extraction of DNA:
Before the DNA can be analyzed, the sample that was collected has to be removed (“extracted”) from the tape or swab.

  • What technique was used to extract the potential DNA sample from the tape or swab?
  • Was DNA extracted from the swab while it was still wet or was it frozen or allowed to dry first?
  • Has the analyst been proficiency tested in collection techniques?
  • Was the “touch DNA” sample kept away from standard samples such as blood cards or cheek swabs to minimize cross contamination?
  • Are there additional measures used in the lab to prevent contamination?
  • Was the analyst aware that he/she was dealing with a “touch DNA” sample?

At this stage, exact copies of the DNA are made so that there will be a sufficient amount of DNA to analyze.

  • Is quantity of DNA measured prior to amplification? Although the starting DNA material recovered from a “touch” sample can be miniscule, current standard laboratory techniques are capable of providing a measure of such small samples.
  • Is any portion of the sample retained for possible further analysis?
  • In amplification, are Low Copy Number techniques used, such as increasing the number of cycles of amplification? Increasing cycle number has drawbacks and can result in artifacts.
  • Did the analyst conduct simultaneous reaction standards and appropriate negative controls to show that no cross contamination occurred in the lab?

This is the most subjective phase of DNA analysis. It is possible for different analysts to reach different conclusions about interpretation, especially where such small amounts of DNA are involved. Consider asking a qualified DNA expert to validate the lab’s data and interpretation.

  • What are the interpretation guidelines? What are the guidelines and procedures for interpreting mixtures? What were the threshold levels for validating a peak as a true allele?
  • How are problems such as allele drop out and allele drop in dealt with?
  • Did the analyst or lab supervisor properly annotate artifact peaks (peaks that are not true genotypic alleles), off-ladder peaks, and other rare allele variants that sometimes show up in the data?
  • How does the analyst account for the potential for transfer of the material and possible artifacts that may confuse the true result?

If touch DNA plays a role in one of your cases, a good starting point to learn more about it is the article, Roland AH van Oorschot et al., Forensic trace DNA: a review, 1 Investigative Genetics 14 (2010).

Click here to access a database of experts in DNA analysis.

Visit the DNA Resources page of the IDS Forensics website for additional information.

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