Wednesday, November 29, 2017


With the use of DNA evidence increasing across the United States, DNA labs are using probabilistic genotyping to analyze hard-to-interpret samples. However, some scientists and lawyers worry that the privately held computer code behind these tools is limiting its reliability and hindering due process.
Traditional DNA analysis is challenged when there are multiple contributors to a sample or the quantity of DNA recovered is too small. Without a better analytical tool, these samples are often inconclusive, says Dan E. Krane, a professor of biological science at Wright State University.
Probabilistic genotyping is not a technique that defines the sample itself; rather it is an interpretive software that runs multiple scenarios—like the risk analysis tools used in finance—to examine the sample. This contrasts with traditional DNA analysis, which assesses whether a DNA type is present or absent.

Bjorn Sutherland, forensic development manager at the New Zealand-based Institute of Environmental Science and Research—a probabilistic genotyping company—says that his software, STRMix, “enables users to compare the results against a person or persons of interest and calculate a statistic, or ‘likelihood ratio,’ of the strength of the match.”

By leveraging computer processing, probabilistic genotyping “gives us more information to work with,” says Chris Lindberg, a deputy district attorney in San Diego. Many, like Lindberg, are excited for this technology because it analyzes samples in a way that would have been too labor intensive previously. The cost of these tools varies by company and number of licenses purchased.
Last year, San Diego joined jurisdictions in Indiana, Louisiana and New York, among others, deploying this technology in its investigations. Sutherland says this technology has been around for less than 10 years, but the statistical models the tools use have been around for decades.
This science has created a cottage industry. Besides STRmix, those receiving the most attention in the U.S. are the Forensic Statistical Tool, used by the Office of the Medical Examiner in New York, and TrueAllele, created by the Pittsburgh-based company Cybergenetics.

The September 2016 PCAST report on forensics noted that “probabilistic genotyping software programs clearly represent a major improvement over purely subjective interpretation.” However, the report added, “careful scrutiny” is still needed to determine whether methods are scientifically valid and if the software correctly implements those methods. The report clarifies that analyzing the software “is particularly important because the programs employ different mathematical algorithms and can yield different results for the same mixture profile.”

Monday, November 6, 2017


An interesting development in the area of algorithms being used to generate statistics on DNA:

A federal judge unsealed the source code for a software program that was used to compare DNA samples in New York City’s crime lab. In July 2016, Judge Valerie Caproni of the Southern District of New York determined in U.S. v. Johnson that the source code of the Forensic Statistical Tool, a genotyping software, “is ‘relevant … [and] admissible’” at least during a Daubert hearing—a pretrial hearing where the admissibility of expert testimony is challenged. Caproni provided a protective order at that time.

This week, Caproni lifted that order after the investigative journalism organization ProPublica filed a motion arguing that there was a public interest in the code. ProPublica has since posted the code to the website GitHub.

Probabilistic genotyping is used when comparing complex DNA samples, like mixtures. It does not define a DNA sample itself; rather, it is an interpretive software that runs multiple scenarios, like risk analysis tools used in finance, to analyze the sample. This contrasts with traditional DNA analysis, which analyzes whether a DNA type is present or absent.

While there are numerous public and proprietary genotyping software programs, ProPublica reports that the “FST was used to analyze crime-scene evidence in about 1,350 cases over about 5½ years.” The FST was phased out at the beginning of this year with the adoption of different software.

Saturday, September 30, 2017

Upcoming Supreme Court Argument--Stored Communications Act

Attorneys interested in electronic communications privacy issues should take note of a case currently under consideration by the Supreme Court that implicates the Stored Communications Act (SCA).
The court will hear oral argument this term in Carpenter v. United States. Carpenter concerns whether Fourth Amendment protections apply to cell phone “transactional records,” which reveal the location and movements of a cell phone. The case is important because it will reconcile a conflict between the long-standing “third party” doctrine and recent cases recognizing privacy interests in electronic data.

In Carpenter, federal law enforcement obtained the transactional records of defendant Carpenter’s cell phones. Federal agents used the data to determine that Carpenter’s cell phones connected with towers near robberies they were investigating.
Law enforcement obtained those records through a court order under Section 2703 of the SCA. That provision allows the government to compel disclosure of communication “transactional records” based on “reasonable grounds to believe” that the information is relevant to an investigation. This standard is less stringent than the Fourth Amendment’s requirement of a warrant supported by “probable cause.”
In the trial court, the defendant moved to suppress the service records, arguing that the more stringent Fourth Amendment standard should apply to the records. That motion was denied, and Carpenter was convicted.
On appeal, the Sixth Circuit also rejected the defendant’s Fourth Amendment argument, finding that the defendant had no reasonable expectation of privacy in his cell phone records under the “third party” doctrine.

Sunday, August 6, 2017

Dane County Criminal Prosecutions

After successfully trying a too drunk to consent case in January and teaching Evidence this summer at the law school, I'm back. In short, things have completely gotten out of hand in Dane County. While this dysfunction has been apparent to the defense bar for the last two years ( it begin to rear its ugly head after the departures of Deputy District Attorneys Viste and Fallon ---both of whom went to work for the State Department of Justice ), it has finally hit the public media.

Isthmus has honed in on part of the story.  For the recent articles, here is the link   If you are a resident of Dane County, shake your head.