At this point in a New Haven investigation, both the found arms and legs have been conclusively tied to one man.
If you've ever wondered how the police identify found body parts, an ongoing investigation in New Haven provides a case study.
Last month, police found sock-footed legs near the South Street train station in New Haven, then arms. Then they found a torso, decaying, in an abandoned building.
New Haven police said that both the arms and legs have been conclusively tied to Ray Roberson, 54, so far in the investigation. Lab results have not yet come back on the torso.
When police find unknown biological evidence, like in this case, they pass it along to scientists at the Division of Scientific Services of the State of Connecticut for identification. The scientists working in the forensics lab aren’t able to comment on specific cases that are still under investigation, but they spoke to WNPR about the process they use to identify body parts.
The forensic investigation begins as soon as evidence arrives at the lab.
“It comes into the lab to our evidence receiving section, and then it gets transferred to the forensic biology section where they vet the case in the sense of taking samples, cutting, swabbing the evidence and then putting it in a storage,” said Cheryl Carreiro, forensic biology and DNA manager.
Following the initial biological testing -- which looks for things like blood, semen, saliva, or other biological products -- samples are passed on to the DNA unit. Those in DNA use different methodologies for different types of samples.
“It really depends on what type of source is responsible for the evidentiary samples, and then also which specific DNA testing you do would depend on the quantity and quality of the biological sample,” said forensic scientist Dr. Carll Ladd. “Is it fresh tissue? Is it old, skeletalized, or highly degraded remains?”
In the case of a severed limb, the first place the scientists go is the tissue. DNA can be pulled out of bone as well, but that takes longer.
“There are several steps: there is extraction and purification of the biological sample, to get the DNA free from all the other junk that’s associated with the sample. Then you find out the quality and the quantity of the DNA, whether it’s male DNA, female DNA. You then go through an amplification procedure where you’re making exact copies of the material,” said Ladd.
“We call it molecular xeroxing,” said Carreiro.
Amplification is done through a molecular process called a polymerase chain reaction. The process does not make copies of the entire length of the DNA -- that would be an enormous about of molecular material.
Instead, scientists use “sticky” pieces of DNA-like material to pick specific portions of the larger DNA strand and copy them.
Forensic scientists make copies of the portions of DNA that can then be used for short tandem repeat (STR) analysis -- the method of choice for identification of biological material in crime labs.
“Standard STR testing is the most discriminating testing we have available,” said Ladd.
STR looks at the portions of DNA known to differ dramatically between individuals, and the sequences within those portions are used to generate a molecular “fingerprint” of the individual from whom the unknown sample originated. Forensic scientists then compare that result to samples of known origin.
Here's an example of a STR profile:
“The short version is that if you have the same pattern between the evidence and the exemplar, that’s a known, that’s a match. The same pattern means that the tested individual could be the source of the DNA profile that was generated,” said Ladd. “Sometimes you’re able to get knowns -- exemplars -- directly, whether it’s by warrant or voluntary submission, and you can compare the evidence to that kind of known sample. In other instances, you can compare to the DNA database of offender samples.”
Roberson, to whom the arms and legs were matched, had a criminal record, so his DNA was on file in the database. The scientists would compare an unknown sample generated from the body parts directly to the one in the system.
Although Ladd, Carreiro, and their colleagues are in forensics, the processes they use weren't developed with criminal justice in mind.
“The procedures that we use in forensics were first developed in basic scientific research environments,” said Ladd. “What characterizes forensics above and beyond is that there are a lot more rules, a lot more procedures and documentation.”
If DNA continues to roll in from New Haven, the scientists at the Division of Scientific Services will keep up their end of the investigation. If not, they'll turn that case fully over the police and detectives, and head on to the next one.
Nicole Wetsman is an intern at WNPR.
Correction: An earlier version of this report incorrectly identified Ray Roberson as Ray Robertson.
