Commonwealth v. Read — Trial ArchiveTess Chart
Testimony Impact
Tess Chart is a forensic DNA analyst employed by Bode Technology, a private laboratory accredited by ANAB and the FBI. She testified in Trial 1 on Day 24 about mitochondrial DNA analysis performed on a hair sample recovered from Karen Read's vehicle. Her testimony established that the hair sample was consistent with John O'Keefe's mitochondrial DNA profile and that at least 99.89% of the population could be excluded as a possible source.
Notable Quotes From The Record
“So in cases just like this one, where there may not be enough nuclear or autosomal DNA to find, you can go back and try to test for that mitochondrial DNA.”
Explains why mitochondrial testing was used — insufficient autosomal DNA was available from the hair sample.
“So the mitochondrial DNA profile that was obtained from the sample — the hair sample — was consistent with the mitochondrial DNA profile obtained from John O'Keefe. So therefore John O'Keefe cannot be excluded as a possible contributor of that hair.”
The central conclusion of Chart's testimony — the hair sample is consistent with O'Keefe's DNA profile.
“So by not seeing it in the database, this means that we're able to exclude at least 99.89% of the population from being a source of that evidence.”
Quantifies the statistical weight of the DNA match using the EMPOP population database.
Key Moments
- Chart explained that mitochondrial DNA testing was employed because the hair sample lacked sufficient nuclear or autosomal DNA — a common limitation with shed hairs — making the mitochondrial approach the only viable method for generating a profile.
- She presented the central finding of her analysis: the mitochondrial DNA profile obtained from the hair sample was consistent with the reference profile taken from John O'Keefe, placing the hair evidence within the prosecution's narrative that O'Keefe had contact with Read's vehicle.
- Chart quantified the statistical significance of the match using the EMPOP population database, testifying that at least 99.89% of the population could be excluded as a source of the hair at the 95% confidence interval, lending scientific weight to the identification.
- The defense waived cross-examination of Chart entirely, leaving her direct testimony and statistical conclusions unchallenged on the record.