DNA sleuth tracks down suspects, kin
Cold cases, the bane of every law-enforcement agency, have received an invaluable resource due to the relatively recent implementation of a revolutionary scientific sleuth.
Known as forensic genetic genealogy, it allowed Middlesex District Attorney Marian Ryan’s Cold Case Unit, along with the Acton Police Department and several other investigative assets, to identify a suspect in a 2013 rape case.
DNA evidence can play a key role in investigations of cold case violent crimes and in cases of missing and unidentified persons. Searching DNA profiles against the FBI’S Combined DNA Index System (CODIS) can often provide investigative leads.
But when that doesn’t occur, forensic science service providers can take up the slack by using forensic genetic genealogy, a technique that combines traditional genealogy research with DNA analysis.
Forensic genetic genealogy first made headlines for its role in the capture of Joseph James Deangelo Jr., the infa- mous Golden State Killer.
The former police officer committed at least 13 murders, 51 rapes and 120 burglaries across California from 1974 to 1986.
He lived under the radar, save for his notorious moniker, for decades.
But on April 24, 2018, the state of California charged 72-year-old Deangelo with eight counts of first-degree murder based upon DNA evidence investigators derived by identifying members of Deangelo’s family through forensic genetic genealogy.
Closer to home. DA Ryan and Acton Chief Police James Cogan announced Tuesday that nine years after a young woman was sexually assaulted at knifepoint at a commuter rail station in Acton, a breakthrough in the case resulted in the arrest of Christopher Aldrich, 28, of Lunenburg.
He was arraigned on the charge of aggravated rape in Concord District Court. Judge Joseph Hurley ordered the defendant be held without bail after a dangerousness hearing.
On the evening of June 18, 2013, a 22-year-old woman, waiting alone at the South Acton Commuter Rail Station, was approached by a white male. The man, allegedly brandishing a knife, raped her. After the assault, he forced her to throw away her cellphone and fled the scene on foot.
The woman retrieved her phone and called 911. Police responded within minutes, but couldn’t locate the assailant. Transported to a nearby hospital, she was treated by a trained sexual assault nurse examiner. Forensic evidence collected from this examination was sent to the State Police Crime Laboratory, whose chemists developed a detailed DNA profile of the attacker.
But for more than eight years, despite continued investigative efforts by Acton police and the Transit police, the perpetrator remained a mystery.
In 2021, as part of the ongoing investigation, Middlesex prosecutors and police contacted Parabon Nanolabs to conduct a forensic genetic genealogy analysis. This technology can analyze aspects of a DNA profile to identify distant relatives in developing a pool of potential suspects.
Through these efforts, Christopher Aldrich, a distant relation living in relatively close proximity, was identified as a person of interest.
In November of last year, Aldrich was involved in a onecar collision on School Street in Acton. Police conducted an on-scene investigation, and in the process lawfully seized a number of items from Aldrich’s vehicle, including an open bottle of Fireball, a popular cinnamon-flavored whiskey.
Police were able to collect additional items containing the defendant’s DNA. Crime lab technicians were able to develop a major male profile from each item. The profiles were a match to each another, and to the offender profile collected from the victim of the 2013 sexual assault.
The expected frequency occurrence of this profile in the population was determined to be less than 1 in 3 sextillion individuals (1 in 3,000,000,000, 000,000,000,000).
In other words, a virtually perfect match.
“… the victim now knows who is alleged to have committed this horrifying crime. I hope this provides some relief to the victim and her family,” said Chief Cogan in a statement Tuesday.
The fact that the suspect was scientifically turned in by an unknown distant relative adds irony, and implications, far beyond potentially solving this cold case.
A 2018 Science.org article indicated that for those Americans of European ancestry, there’s a 60% chance you have a third cousin or closer relative contained in the Myheritage database, which contains 1.28 million DNA profiles of individuals looking at their family history.
The same result will likely come from searching Gedmatch, a genetic genealogy research website, which only encompasses about 0.5% of the U.S. adult population.
If that Gedmatch pool rises to just 2%, it’s projected that 90% of Americans of European descent will have a third cousin or closer relative in that database.
Relatively speaking, it seems we’re all one big family.