New DNA testing technique exonerates man 20 years into 30-year sentence

The method identified a new suspect who has now confessed to the crime

The new DNA evidence led police to arrested Brian Dripps in May. AP

Two decades into his 30-year sentence for murder, Christopher Tapp has been exonerated thanks to evidence brought to light by the new method of marrying up DNA and genetic family tree information.

He is the first person to have a conviction overturned using the revolutionary new investigative technique.

Mr Tapp, now 43, was convicted for the rape and murder of Angie Dodge in 1996 and sentenced to 30 years in prison.

Then on Wednesday, a court in the state of Idaho completely overturned his conviction when presented with evidence found by tracing genetic genealogy that matches DNA to the suspect by searching through records of distant relatives. It is the same technique used to identify a new suspect in the "Golden State Killer" case that led to charges being filed last April.

"It's a new life, a new beginning, a new world for me, and I'm just gonna enjoy every day," local media quoted Mr Tapp as saying at the end of the hearing.

Mr Tapp's exoneration came after police arrested another suspect, Brian Dripps, in May. Dripps was identified using genetic genealogy and then confessed to the crime.

The new technique first made headlines in April 2018 when it was used to find the alleged "Golden State Killer" in California. The man is blamed for 12 murders and more than 50 rapes dating back to the mid-1970s and – until now – police had few concrete leads.

The case is one of about 70 that have been solved since when DNA found at crime scenes was compared to the databases for genealogy websites.

The websites – widely advertised in the United States – allow users to post DNA test results and then generate a list of people with similar genomes, enabling users to find distant relatives and trace family backgrounds.

But the databases also allow police officers to search through people with similar genetic profiles to DNA found at crime scenes. Tracing back through family trees and seeing where the DNA crosses can lead investigators to a suspect even if the main suspect has not themselves carried out such a genealogy test.

But Mr Tapp's case is the first in which genetic genealogy has been used to prove innocence rather than guilt.

"It's just such an incredible feeling to be a part of clearing an innocent man's name," CeCe Moore, the genetic genealogist who worked on the case, said in an interview with ABC.

While the new method carried the case over the line, the evidence against Mr Tapp began to crumble before investigators started to look at the DNA.

In 1998, Mr Tapp was sentenced to 30 years in prison based solely on his confession, which he then retracted.

In 2017, he was freed from prison in a court agreement, but the murder charge was not dropped.

A year later, his defence team obtained the right to test sperm traces found in Angie Dodge's bedroom – the source of the genetic genealogy evidence that led investigators to Dripps.

The new suspect, who in 1996 lived just across the street from Dodge, confessed to the crime after officers tested a cigarette butt he had thrown away against the crime scene DNA.

The Idaho Bonneville County prosecutor withdrew the charges against Mr Tapp and filed a motion to exonerate him, which a judge endorsed on Wednesday.