Category Archives: DNA

NIST urges caution in use of likelihood ratio

The National Institute of Standards and Technology (NIST) released an article last week calling into question the use of the likelihood ratio to present evidence in court. NIST states that there is uncertainty about the appropriate use of the likelihood ratio. An expert’s subjective opinion may affect the calculation of the likelihood ratio, potentially distorting the evidence. More information is available here.

Attorneys who see a likelihood ratio in a lab report should consider the NIST report and  investigate further prior to trial. Many labs are moving toward implementation of the likelihood ratio for interpretation of DNA analysis. To my knowledge, the NC State Crime Laboratory and the Charlotte-Mecklenburg Police Department do not employ the likelihood ratio in their interpretations of DNA evidence, though it could be adopted at some point in the future. The likelihood ratio is used by some private laboratories, such as NMS Laboratories.


Leave a comment

Filed under DNA, Uncategorized

New Research on “Touch” DNA

As the sensitivity of DNA analysis increases, scientists are able to develop profiles from ever-smaller samples of DNA. This has lead to testing of a wider array of samples collected from crime scenes, including window panes, bullets, hats and other clothing, cigarette butts, and many other items.

Attorneys sometimes ask me about the likelihood of obtaining a useful DNA profile from certain items of evidence. A study from six European forensic laboratories may give some idea of how likely it is to find a DNA profile on items commonly found at crime scenes. This article contains an interesting chart that lists the item and the likelihood of finding a full profile, usable partial profile, possibly usable partial profile, or no profile. It seems best to use this type of information as a rough guide, but it is interesting nonetheless.

It is important to keep in mind that as labs are able to analyze smaller amounts of DNA, the possibility of developing partial profiles and complex DNA mixtures increases. Where very small amounts of DNA are involved, the sample may have been deposited by secondary transfer. Here’s an interesting article on secondary transfer and “touch” DNA.

Attorneys should be aware that forensic laboratories may have case submission guidelines that limit the number and type of items that may be tested by the lab. To understand why and how an item was tested (or not), it is important to read the lab’s policies and guidelines. Here is a link to the North Carolina State Crime Lab’s Evidence Guide. There is information about Touch DNA testing on p. 52.


Filed under Crime Labs, Crime Scene, DNA

Familial DNA Testing

by Emily Zvejnieks

Familial DNA testing, an innovative yet highly controversial technique, is being used in several states. This blog post will provide an explanation of what familial DNA testing entails and briefly discuss its Fourth Amendment implications.

In standard DNA testing where there is an unknown sample, that unknown sample may be compared against samples in the Combined DNA Information System (CODIS), an index maintained by the FBI. The index is made up of samples of convicted offenders and individuals who have been arrested or charged with certain crimes but not yet convicted. Traditionally, the unknown sample is compared against known samples in the database, looking for an exact match.

In situations where an unknown sample exists but a search of an existing DNA database returns no exact matches, it is possible to conduct a search to identify potential relatives of the alleged perpetrator. This process is called familial DNA testing. The actual process is a low-stringency search, which produces inexact matches. The search is based on the idea that those closely related to each other share more genetic data than those not closely related.

There are two pending U.S. cases currently in the spotlight where defendants were identified as a result of familial DNA testing in California and Wisconsin. Lonnie Franklin, Jr., also known as the alleged “Grim Sleeper” serial killer, is charged with several counts of murder for crimes that occurred in Los Angeles in the 1980s and 2000s. In that case, authorities obtained the perpetrator’s DNA from various crime scenes. After running the DNA through the offender database with no exact matches and no other suspects, the sample was submitted for familial searching, and the search rendered a result of a potential first-degree family member. Detectives then determined that Lonnie Franklin, Jr., the father of the person whose DNA sample was in the database, lived in close proximity to most of the crime scenes.  An undercover officer then followed Franklin to a local pizza joint and, after Franklin was finished with his plate, collected his plate, pizza, and utensils. After testing DNA obtained from his leftovers, authorities matched the unknown sample to Franklin. Franklin has since been charged with ten counts of murder and one count of attempted murder, and his cases are pending.

Wisconsin recently used familial DNA testing for the first time. The case involves pending sexual assault charges against Michael L. Dixon.  A series of similar rapes that occurred between 2008 and 2012 in Milwaukee remained unsolved until a familial DNA search was performed using the perpetrator samples from the crime scenes. Using familial DNA testing, there were two close matches. Upon further investigation, it was determined that one of those matches did not have any male first-degree relatives, so that possible match was eliminated. The other close match did have a brother: Michael L. Dixon, who had been found not guilty of a 2012 rape with similar facts to the unsolved rapes. Wisconsin authorities had Dixon’s DNA sample from his arrest on the 2012 charges, but his DNA was never added to CODIS since he was not convicted. The perpetrator’s DNA from the unsolved rapes and Dixon’s DNA were an exact match. Dixon now awaits trial for first and second degree sexual assaults.

The Innocence Project opposed the use of familial DNA testing in a February 2013 position paper.  Interestingly, California implements many of the safeguards the Innocence Project suggests regarding admissibility of evidence procured through familial DNA testing. Michael Chamberlain, Deputy Attorney General of the California Department of Justice, wrote an article published by the American Bar Association in 2012 that lays out familial DNA testing use and practice.  California uses its own software called the “ratiometer.” After coming up with 150-200 possible close matches, the ratiometer runs a Y-STR test, which analyzes the Y chromosome only to determine whether there is a matching Y-STR profile. If Y-STR profiles match, that indicates there is a paternal relationship. Because the California process uses the Y-STR test, familial DNA testing cannot be used for females and also does not identify half-brothers who share the same mother.

Fourth Amendment implications of familial DNA testing are mind-boggling.  On one hand, we know that a defendant does not have a Fourth Amendment claim when his or her privacy interests were not violated.  Many of the samples entered into CODIS belong to convicted felons who, according to our justice system, gave up some privacy interests by way of their actions.  Familial DNA testing is a search of those samples.

On the other hand, the reason that there is no exact match in the CODIS database and familial DNA testing is being done is because the suspected perpetrator is not a convicted felon and thus his or her privacy rights have not been compromised.  Each person shares DNA with his or her parents, siblings, and children.  If one of them has given a sample due to being a convicted felon, or even gives a sample voluntarily, then their relatives’ DNA can be analyzed as well.

Arguably, familial DNA searching falls under the “technology not in general public use,” as discussed in Kyllo v. United States. In Kyllo, SCOTUS held that a thermal imaging device used to determine excess amounts of heat inside a private residence was a search as the technology employed was not in general public use.  Kyllo, 533. U.S. 27 (2001). Similarly, DNA searching is a technology not in general public use, and it could be argued that familial DNA testing is a search requiring a warrant – otherwise it would be a way for the government to get around Fourth Amendment protections of a person whose family member’s DNA is in a database.

Another concern with the use of familial searching is that it will create suspects out of innocent people simply because they are related to someone whose DNA is in a database and their relative’s DNA is similar to DNA found at a crime scene. Because of the racial makeup of the existing DNA databases, people of color will be disproportionately impacted. Innocent citizens will become subjects of police investigation, and will bear the privacy, emotional, economic, and liberty costs associated with being investigated for a crime.

As familial DNA searching becomes more widely used in the United States, it will be interesting to see what North Carolina as well as the Supreme Court of the United States decide on its use and admissibility. To date, the only known case where this technique has been used in North Carolina is the Darryl Hunt case. Certainly any jurisdiction choosing to perform familial DNA testing should implement stringent requirements for its use. For more information, this website offers a four-part webinar series on familial DNA testing.

Other Sources:

42 U.S.C. 14132.

Kyllo v. U.S., 533 U.S. 27 (2001).

Bruce Vielmetti, First use of Familial DNA test leads to charges in serial sex assaults, Milw. J. & Sent., July 11, 2014,

Chamberlain, Michael, Familial DNA Searching: A Proponent’s Perspective, Crim. Just., Volume 27, Number 1, Spring 2012.

FBI, Familial Searching,

Global Justice Information Sharing Initiative, An Introduction to Familial DNA Searching for State, Local, and Tribal Justice Agencies: Issues for Consideration,–Local–and-Tribal-Justice-Agencies.

Kim, J., Danny Mammo, Marni B. Siegel, and Sara H. Katsanis, Policy Implications for Familial Searching, Investig. Genet., November, 1, 2011.

Symposium, Family Ties:  The Use of DNA Offender Databases to Catch Offenders’ Kin, 34 J.L. Med. & Ethics 248 (2006).

Weiss, Lindsey. All in the Family: A Fourth Amendment Analysis of Familial Searching.  The Selected Works of Lindsey Weiss.  Available at:

Leave a comment

Filed under DNA

Changes to Protocols for DNA Interpretation

Recently, the State Crime Lab has undergone several rounds of changes and updates to their protocols and standard operating procedures (SOPs) for the analysis and interpretation of DNA evidence. Attorneys should be aware of these changes and that only cases worked on or after the effective date will be subject to the new policies.  Previously-worked cases will not be reevaluated by the Lab to determine whether the new policies would have resulted in any change(s) to the conclusions drawn. Three changes are worth noting in the most recent update (Procedure for Casework DNA Interpretation, Effective Date: 03/08/2013).

First, the Lab has changed their Analytical Threshold (also known as the detection threshold) from 75 RFUs to 50 RFUs. This threshold is similar to a cutoff value and is determined empirically by the lab through internal validation studies. In general, any allelic peaks in a DNA profile (as seen on an electropherogram) that pass that threshold are considered to be true alleles or artifacts and not background noise. Under previous protocols, peaks below 75 RFUs were considered to be below detection but were sometimes evaluated for the potential exclusion of individuals. By lowering the detection limit to 50 RFUs, the lab can interpret more information from low quality samples and/or mixtures where minor contributor(s) is/are present.

Second, in accordance with national guidelines that have been in place since 2010, the Lab has implemented another threshold known as the Stochastic Threshold. In essence, this threshold defines another cutoff value that is higher than the Analytical Threshold and provides the analyst with a zone of uncertainty in the DNA analysis data. This threshold (currently set at 200 RFUs) is also determined by the Lab through internal validations. Allelic peaks that pass the detection threshold but fall below the stochastic threshold (above 50 RFUs and below 200 RFUs) are said to be in Stochastic Effect, which is another term that refers to the technically-induced random loss of allelic data from a given DNA profile (also known as allelic dropout). Stochastic Effect is often caused by low DNA quantity and/or quality in a given sample.  For rendering interpretation from mixture profiles in particular, the Lab will no longer include allelic peaks that are in stochastic effect in their statistical calculations. (See Procedure for Statistical Calculations, Effective Date: 08/08/2013)

Third, the Lab has implemented a new empirically-derived value for what is known as allelic imbalance, a term that defines whether DNA alleles at a given marker/locus are representative of one or more individuals. This value is calculated by dividing the RFU value of the lower peak by the RFU value of the higher peak and expressing the number as a percent. After using a value of 50% for the past 5 years, the Lab has now implemented a new value of 65%. Alleles that are 65% (or higher) of RFU value from each other are said to be balanced (indicative of a single contributor).  If that percentage is lower than 65%, then there is an indication of allelic imbalance which plays a significant role in the interpretation of mixture profiles.

It is worth noting that the Lab has implemented a flow chart to be utilized by the analysts for DNA profile comparisons and interpretations (See Procedure for Casework DNA Interpretation, Effective Date: 03/08/2013, p. 10) and that the new SOPs reflect the Lab’s adoption of newer-generation kits for forensic DNA testing.  The three major changes described above can have a significant impact on the interpretation of DNA evidence and the overall conclusions reached by the Lab analyst in the course of analyzing evidence samples in general, and mixture/partial profiles in particular. Cases analyzed on or after March 8, 2013, will follow the new procedures. Cases analyzed previously will follow the older procedures and new conclusions will not be rendered on cases analyzed under the old procedures.  Defense counsel are encouraged to do further research or seek the assistance of a DNA expert to evaluate whether those changes (and other modifications to the SOPs) have a bearing on their cases.

Leave a comment

Filed under DNA, Uncategorized

NIJ Study of Near Misses and Wrongful Convictions

The National Institute of Justice recently released their study Predicting Erroneous Convictions which examines why some innocent people are wrongfully convicted while others are acquitted, using a case comparison method rather than a traditional “case study” method. Researchers at American University who compared a group of 260 cases that occurred between 1980 and 2012 where an innocent defendant was exonerated only after conviction with a control group of 200 cases where an innocent defendant was acquitted or had charges dismissed before trial.

Unlike prior studies which have focused on what causes an innocent defendant to be charged, this study’s results can be used to determine what is preventing the innocent defendant from being acquitted or having charges dismissed once in the system. This is a helpful distinction, as it allows a greater focus on criminal defense, forensic practices, and prosecutorial discretion.

A Mixed Method Approach

The study’s quantitative analysis yielded 10 primary factors that led to a wrongful conviction rather than the “near miss” dismissals and acquittals:

  • A younger defendant
  • A criminal history
  • A weak prosecution case
  • Prosecution withheld evidence
  • Lying by a non-eyewitness
  • Unintentional witness misidentification
  • Misinterpreting forensic evidence at trial
  • A weak defense
  • Defendant offered a family witness
  • A “punitive” state culture

A qualitative analysis of the data followed in which a panel of criminal justice experts analyzed 39 cases to determine how the ten factors were connected and whether “tunnel vision” (when law enforcement professionals focus more on building a case against one suspect at the expense of ignoring contradictory evidence) played a role.

The final report offers recommendations to prevent future wrongful convictions, including recommendations on defense practice, exculpatory evidence, eyewitness identification, false confessions, forensic error, police misconduct, weak prosecution evidence, systemic failures and tunnel vision. The report emphasizes that the interactions of these factors as much as the individual factors themselves are to blame for systemic breakdowns leading to erroneous convictions. This type of interaction requires a comprehensive approach to reform in order to prevent future errors.

Traditional Wrongful Conviction Factors

Factors that have traditionally been suggested as sources of erroneous convictions, such as false confessions,  witness misidentification, and racial bias, appeared at statistically similar rates in both sets of cases. Thus, these factors likely only increase the chance that an innocent suspect will be charged but not the likelihood that the charge will result in conviction rather than dismissal or acquittal.

Forensic Error as a Primary Factor in Wrongful Convictions

As one would expect, this study revealed that errors in forensic evidence were correlated with an increased likelihood of erroneous conviction. However, this study’s results suggest a new perspective on how forensic error impacts case outcomes. Errors in forensic testimony, rather than errors in the actual testing were the most common source of forensic error.  Forensic testimony errors include: not providing the jury with key forensic information, overstating the inculpatory nature of evidence, use of inaccurate statistics, and misstating the certainty of results and forensic techniques. The implication is that an emphasis on quality control at the interpretation and testimony stages should be added to previous policy recommendations that have focused on improving quality of forensic lab procedures.

While DNA is a widely respected as a forensic tool, this study found that the prohibitive cost of DNA testing often renders it a tool of last resort, with other less accurate forensic tools like fingerprinting, hair comparison analysis and serology testing being used first.

Recommendations for Improving Forensic Error

  • Timeliness: Forensic investigation, especially DNA testing, should be conducted early in a case to rule suspects in or out, rather than later once an investigation gains steam and there is a danger of it being used more to confirm or check what police/prosecutors already believe.
  • Training/Education: Prosecutors and defense attorneys need more education about forensic testing techniques and should get clarifications about results if they do not fully understand a report. Police officers in more jurisdictions need to be trained in crime scene investigation and should then be present when technicians are collecting evidence to help direct and expand the search.
  • Supervision: Forensic labs should be more closely supervised and have procedures that are peer reviewed. There should be discussions of “near miss” cases, which could follow, for example, in the vein of the morbidity and mortality conferences that the medical community holds to discuss mistakes in patient care.

For more information, watch the forthcoming recording of the Wrongful Convictions seminar given by the report’s authors, found here.

1 Comment

Filed under Crime Labs, DNA, Resources

BBC Knowledge Explainer DNA

Here is a 3-minute video that explains the basics of DNA’s form and function. It’s part of the BBC’s online Explainer documentary series. Though the focus of this short animated film is not forensic DNA analysis, it gives important information that attorneys or jurors need to understand before attempting to understand forensic DNA analysis. Attorneys should watch the video for their own information and also to think about whether this information is being communicated effectively to jurors by DNA experts.

Leave a comment

Filed under DNA

Thousands of cases compromised due to faulty forensic analysis

In recent months, faulty forensic analysis has been exposed in several labs across the country. The failure of a handful of lab analysts to correctly perform forensic analysis has compromised thousands of cases. In each situation the failures are different, but they expose a lack of oversight of analyst performance in the affected labs. The following are several of the most serious failures:

Annie Dookhan

A Massachusetts chemist was accused of faking test results at the state lab and tampering with drug evidence while she tested suspected controlled substances in criminal cases. Authorities declared that Dookhan tested more than 60,000 samples involving 34,000 defendants during her nine years at the Department of Public Health lab. Over 200 convicted defendants have been released from custody while their cases are being reviewed due to Dookhan’s involvement, according to this article. One of the red flags that lead to Dookhan’s misconduct being detected was the fact that she was highly efficient at her job; she was handling an astounding number of samples compared to an average chemist. Investigators allege that Dookhan was able to accelerate her work by “dry labbing” or reporting results for analyses that she did not actually perform. Dookhan has been indicted on 27 charges, including 17 counts of obstruction of justice, eight counts of tampering with evidence, perjury and falsely testifying that she held a degree from a college or university.

Sonja Farak

Another Massachusetts chemist that worked in the state crime lab in Amherst was arrested in January and charged with evidence tampering and possession of controlled substances from the lab, according to this article. The Boston Globe reported that Farak was discovered when her supervisors were making a routine check of tested substances and found that certain substances tested by Farak had been replaced with counterfeit substances. Attorney General Martha Coakley said that both Farak and Dookhan had begun their career at the Hinton lab in Jamaica Plain. Unlike in Dookhan’s case, supervisors noticed that Farak had had a drop in her productivity. Authorities have stated said that Farak’s misconduct was quickly detected by her supervisors, limiting the scope of its impact.

Jonathan Salvador

A forensic scientist who worked as a controlled substances analyst at the Texas Department of Public Safety (DPS) was suspended when it was discovered that he issued a fraudulent report about a batch of pills, according to this post in the Grits for Breakfast blog. The report was issued without testing the pills and instead, substituted data from another sample. The DPS characterized Salvador’s work as deficient prior to this incident. Case supervisors were aware of Salvador’s poor performance and knew that he appeared not to understand the science of the work he was assigned. However, his performance was tolerated and he would often volunteer for unwanted tasks in the lab. In its internal investigation, the DPS found several additional cases where Salvador misreported results. According to Grits for Breakfast “hundreds of convicted defendants may end up having their cases overturned, either freeing them from prison or ending their probation terms.” It was reported that hundreds of samples tested by Salvador during his six years at the DPS were being retested.

Iowa analyst fired over mishandling of fingerprint evidence

A state police crime lab analyst in Iowa was fired in January due to errors in reports related to fingerprint analysis, according to this article. The lab reviewed the analyst’s 2012 cases and found at least nine cases contained errors where the analyst had incorrectly classified fingerprint evidence as unusable. The analyst’s errors were discovered in a routine internal review of cases. The investigation of the analyst’s casework continues. The analyst had been employed by the lab for sixteen years.

Mishandling of DNA Evidence in Rape Cases

The New York City Medical Examiner’s Office is reviewing over 800 cases worked by a lab technician who resigned in 2011. According to this New York Times article, reviewers have found so far that the technician failed to detect biological evidence in 26 cases when in fact existed. Additionally, in 55 cases, the lab technician failed to upload evidence from crime scenes into the state’s DNA database. The mishandling of DNA evidence led sex-crime investigators to not have available evidence that was could have been used to develop cases against rape suspects.  Supervisors also discovered sixteen pieces of evidence that had been placed in the wrong rape kits. The majority of the misplaced items were swabs sealed in paper envelopes.  This mixing of items from different cases raises concerns about cross-contamination and whether other lab protocols were ignored.

Additional cases of lab analyst misconduct are detailed in this NACDL News Release.

In sum, it is important for the attorneys to be aware of the risks of not reviewing the lab reports, including the underlying data, in all of their cases. Although the majority of labs endeavor to monitor the work of individual analysts through case reviews, the cases above indicate that supervision cannot completely deter deficient performance by individual analysts.

Leave a comment

Filed under Crime Labs, DNA, Drug Analysis/Toxicology