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TOOELE — Investigators say a new technique involving DNA evidence — one that the Utah State Crime Lab has only used twice — helped them solve a brutal 2011 beating death of a Tooele woman.
Murder and other criminal charges were filed Monday against Rogelio Diaz Jr., 23, in the Oct. 7, 2011, death of Evelynne Derricott, 69. He is accused of striking the woman multiple times with a hammer in her Tooele home, 410 Havasu Dr., when he was 18.
At the crime scene in Derricott's house, a Stanley hammer was found with red/brown staining. The staining was later identified as human blood. The hammer was sent to the state crime lab for analysis. The DNA of an unknown male was found on the hammer in addition to Derricott's DNA.
A day after her body was discovered, Derricott's car was found abandoned in Kearns with her cellphone inside. DNA collected off the steering wheel matched the male DNA found on the hammer, according to an arrest affidavit.
But the DNA that was collected did not match anyone in the Combined DNA Index System, or CODIS, a database of offenders who have been convicted of certain types of crimes. Currently, there are approximately 110,000 DNA records of Utah offenders in the CODIS system.
Because the unknown DNA was that of a male, the state crime lab agreed to do familial DNA testing.
Utah State Crime Lab Director Jay Henry said if investigators have a sufficient DNA sample — and if it is male, and all other leads have been exhausted — then they can test it to see if there any potential relatives of the unknown sample in the CODIS system.
According to one study, Henry said about 46 percent of inmates also have a relative who is in the corrections system.
"So the theory behind that is, if you don't have the crime scene profile — that defender is not in the database — maybe a family member is. And from that, you can generate an investigative lead that can lead you to the true perpetrator," he said Monday.
The familial DNA testing only compares those samples collected in Utah. The testing is only for male suspects, Henry said. There is an equivalent test for female DNA, he said, though it has not been done in Utah. He noted that based on the numbers, there is a greater chance of a suspect being male.
Henry called the familial DNA testing a "last resort."
"It is time-intensive. It is resource-intensive," he said.
In the two years since the Utah State Crime Lab has had the ability to do familial testing, Henry said it has only been done twice, though he declined to say in what cases it was used.
Once the familial DNA test finds a match of possible relatives, such as a brother, father or son, it's then up to a the police department investigating the crime to narrow the list of possible suspects by doing additional police work.
In the Diaz case, the Tooele police detective in the case wrote in his arrest affidavit that after receiving the results of the familial DNA testing, he got a lead that eventually led him to Diaz.
Investigators began watching Diaz, and on April 22 they collected a pair of work gloves he had left on the ground and a Rockstar Energy can he had drank, according to the statement. Both were sent to the crime lab.
"The DNA profile from the can matched the unknown DNA profile found on the hammer," the affidavit states.
Diaz was charged Monday in Tooele County's 3rd District Court with murder, a first-degree felony; aggravated burglary, a first-degree felony; and theft, a second-degree felony.
His initial appearance is scheduled for Wednesday.
Contributing: Jed Boal
