YUMA, Ariz. - An expert in DNA forensic analysis told the jury she found Preston Strong's DNA on the steering wheel of Luis Rios' Dodge Durango, in day 15 of the La Mesa Street Murders trial.
According to Lorraine Heath, previously with the Arizona Department of Public Safety's (DPS) Crime Lab, DNA from at least four people was found on the Durango's steering wheel.
Rios' Dodge Durango went missing from the home shortly before police arrived on June 24, 2005, the night of the incident.
The prosecution alledges the suspect used the Durango as his getaway car.
On Tuesday, Heath told the jury that detectives collected and sent her six swabs with DNA evidence from the steering wheel.
"Now the police took swabs from various places in the Dodge Durango," prosecutor John Tate told the jury during opening statements on February 7, "These were sent to the DPS crime lab for DNA analysis by a scientist at the Department of Public Safety. Her name is Lorraine Heath and she created a profile from that DNA that was matched to a profile of Preston Strong."
On Tuesday, Heath confirmed Tate's explanation. However, she only considered three of the individuals to be "major contributors".
"When I look at the profile of more than one person, the information can tell if there is more DNA than another person. It is very dependent on the actual item, but we call those with more DNA "major contributors" or "significant contributors"," Heath told the jury.
Heath said Rios, Strong, and a third unidentified person were considered "major contributors".
"Luis Rios was definitely considered a significant contributor, as is expected for the owner of the vehicle," Heath explained.
Moreover, Strong's DNA was also greatly represented in the sampling.
"We also assign a weight to the decision so, in this case, we believe it is 9 million times more likely the three contributors' DNA belonged to Rios, Strong and an unknown person than if it was Rios and two unknown Hispanic individuals," Heath explained.
According to Heath, when she first tested and found the DNA, she didn't know it belonged to Strong.
"I initially didn't have Strong's DNA to reference it with. I wrote it down as a larger foreign contributor that wasn't Rios. Later when I got Strong's swab, I was able to match Strong to the steering wheel," Heath explained.
Heath said that she tested the DNA on August 25, 2005.
A sample of Strong's DNA was sent to her in late March of 2006. She created his profile on April 5, 2006 and identified him as the second "foreign contributor".
Heath said there was a fourth, or possibly more other minor contributors, whose DNA was found on the steering wheel.
"I wouldn't say the total number was eight, but it was at least four total contributors including minor contributors," Heath explained.
While Heath said she couldn't determine when the DNA was left by a person, she said the more of the person's DNA that is found, the higher they were the last to touch it, especially on something like a steering wheel.
"The steering wheel, for example, was handled a lot by the owner. Right after he touched it, his DNA would be there and if I were then to touch it, I will start rubbing off his DNA and adding mine," Heath explained, "Assuming the vehicle is in routine use by the owner, I would expect another significant contributor handled the vehicle fairly recently."
During cross examination, the defense questioned Heath about the DNA extraction process in 2005 and its evolution since then.
Heath answered that the process for extraction had remained the same, but new procedures in documentation had been implemented.
"I would say I am more likely to document more steps now, than I did then. We are encouraged to write more down," Heath said.
Heath added that per standard procedure, her findings were also peer reviewed by another colleague before being shared with detectives.
The defense also questioned Heath about the number of people whose DNA was tested in reference to the steering wheel.
Heath replied there were 18 total references.
Javier Frigo, Luis Leal Morisca, Raya Shaya, Kimberly Cole, Carlos Banda, Lester Cornelius, Michael McCormick, Arturo Romero and Susan Mejia were ruled out as being possible "significant contributors".
Diego Cisneros, Rebekah Rios, Danny Heredia, Inez Newman, Enrique Bedoya and Andreas Crawford, were ruled out as being "significant contributors" but were given inconclusive results in reference to them being possible "minor contributors".
"I can't say for sure that they aren't or that they are minor contributors, but they are excluded from being major contributors," Heath explained.
Defense Attorney Raymond Hanna further questioned Heath about other evidence items submitted for DNA testing.
Heath said she tested several other items and looked for matches with Strong's DNA but found none elsewhere.
"Strong's DNA was excluded from the 35 other items," Heath said.
A juror also asked about the DNA found on the other items.
"Many of the items collected matched the victims. There were few items with foreign DNA," Heath answered.
"Bindings are difficult to analyze from a DNA perspective. It is hard to get foreign DNA. Typically you just get the person that was bound. We figure one possibility for this is because there is so much friction from the person being bound, so the other DNA rubs off," Heath continued.
Heath said that the foreign DNA that was found on some of the items and bindings submitted could have come from any source, including detectives.
"It could be anything from the time the binding was removed to talking over things [evidence]," Heath explained," We don't like to think we are spitting when we're talking but we totally are."
Heath said trace levels of foreign DNA were found on 6-year-old Danny Heredia.
"But like I mentioned, they could come from anywhere," Heath said.
Yuma Police Department Lieutenant Wayne Boyd also took the stand on Tuesday.
Day 16 of the trial resumes on Monday, March 20.