Saturday, November 26, 2016

People v. Ramsaran: How Not to Evaluate a DNA Mixture

Did Ganesh Ramsaran kill his wife, Jennifer, after dropping their children off at school on a chilly morning in December 2012? At around 7:54 that night, he called the police and told them that Jennifer was missing. He said she had left their home in New Berlin, New York, at 10 that morning to go shopping in Syracuse, about 60 miles away. He expected her home at around 5:00 p.m.

When she did not show up, he wasted little time. At 5:30,  he called his father-in-law to say that he was going to call the police. When he called the police a few hours later, he was “adamant something terrible had happened.” He said they had a perfect marriage.

A program manager for IBM, Ganesh later told police that, after returning from the school, he worked from home on his computers. However, a forensic investigator determined that one of Ganesh's work computers was not used at all that day and the other was not used between 8:08 a.m. and 6:31 p.m. (except for the automatic installation of new software before 8:25 a.m.).  Jennifer had been playing an online game until about 8:15 a.m., when she abruptly ceased playing. She had told her online game partner that she was not going to Syracuse until later in the week because her van was making strange noises. Video footage undermined Ganesh’s account of having gone for a run to the Y that morning. As for the perfect marriage, there was evidence of a divorce in the air, an extra-marital affair, and even an insatiable sex drive.

Five days after the disappearance, the van was found in an apartment parking lot. Two months later, Jennifer's naked and decomposed body was found at the bottom of an embankment, with bruises and lacerations, bleeding underneath the scalp, and internal hemorrhages across the back.

Ganesh was tried for murder. In addition to the facts given above, DNA evidence supported the verdict of guilty. “Large blood stains in the back of [the van] were a conclusive DNA match with the victim,” and she “could not be excluded a contributor” to a blood stain on the sweatshirt that Ganesh had worn the day she disappeared. A “forensic expert testified that it was 1.661 quadrillion times more likely that the blood sample from the sweatshirt contained a combination of defendant's and the victim's blood than if two randomly selected individuals were the donors.”

The appellate division reversed the conviction because of “defense counsel's failure to object to the prosecutor's inappropriate characterization of the DNA testimony and evidence during summation.” The expert, Daniel Myers, had testified that although “the STR/DNA mixture profile ... is 1.661 quadrillion times more likely to be observed if donors are defendant and the victim than if two random unrelated people were selected, ... there were not enough alleles or DNA data to say conclusively that the victim's DNA was present.”

The prosecutor went further “during summation, ... by stating ... ‘on that sweatshirt is [defendant's] wife's DNA’”; that Jennifer’s “DNA was on that area where the bloody spot is”; and that “the forensic people [say that Jennifer's] DNA is on that sweatshirt, to some degree.”

How should the significance of the DNA typing results have been presented? The likelihood ratio for “two random unrelated people” is relevant, since it constitutes one conceivable explanation for the origin of the blood stain on the sweatshirt. If it were the sole “defense hypothesis,” and if the likelihood ratio with that hypothesis in the denominator were anything like 1.661 quadrillion, then the prosecution could maintain that the only reasonable conclusion was that the mixed stain came from Jennifer and Ganesh. Indeed, if the only comparison were between a Jennifer-Ganesh mixture and a nonJennifer-nonGanesh mixture, it would not have been egregiously wrong to suggest that Ganesh’s DNA in the mixture is what the forensic analyst reported “to some degree.”

However, other hypotheses consistent with innocence cannot be ignored. The most obvious is that the contributors were Ganesh and an individual unrelated to Jennifer. After all, Ganesh was wearing the sweatshirt. The hypothesis that the mixed stain was from him and someone besides the victim surely merited consideration along with the less probable hypothesis that the DNA from from neither Ganesh nor his wife. Without revealing how the likelihood for that defense-compatible hypothesis compares with the likelihood for the prosecution's claim of a Jennifer-Ganesh mixture, the state withheld information necessary to a fair assessment of the DNA evidence.

Prosecutors have license to present their evidence for all that it is worth, and the prosecutor in this case may have believed that the likelihood ratio of 1.661 quadrillion was the appropriate measure of probative value. But to know what the bloodstain on the sweatshirt really proves, one must consider all the relevant alternatives to the state’s claim about the evidence. There is no indication in the opinion that the jury was given the information it needed to assess the bloodstain evidence.

Now it could be that the likelihood ratio with the Ganesh-nonJennifer hypothesis in the denominator also would have been outrageously large. But without some indication of the magnitude of that likelihood ratio, the jury was not given a fair picture of the meaning of the mixture.

People  v. Ramsaran, 141 App. Div. 3d 865, 35 N.Y.S.3d 549 (2016)
Joel Stashenko, Panel Orders New Trial for Man Charged in Wife's Death, N.Y.L.J., July 19, 2016

Thanks to Ted Hunt for calling this case to my attention.


  1. Professor Kaye -- I don't know if this would change your analysis, but the sweatshirt in question was worn by the defendant, not his wife. From the Appellate Division, Third Department opinion:

    "Analysis on a blood stain on the sweatshirt that defendant wore on the morning that the victim disappeared concluded that defendant was the major contributor of the blood and that the victim could not be excluded as the minor contributor to that blood stain. Furthermore, a forensic expert testified that it was 1.661 quadrillion times more likely that the blood sample from the sweatshirt contained a combination of defendant's and the victim's blood than if two randomly selected individuals were the donors."

    1. You are absolutely right. I'll revise the statement of facts. The problem with the presentation of the one likelihood but not the other is the same.