Forensic consultant said DNA transfer could explain how Jerry Burns' DNA was found on Martinko's dress

Defense rests after one witness; Burns didn't testify

Michael Spence of Spence Forensic Resources in New Mexico addresses the state of the repackaged case evidence of Michell
Michael Spence of Spence Forensic Resources in New Mexico addresses the state of the repackaged case evidence of Michelle Martinko’s pantyhose and dress during testimony Thursday at the Scott County Courthouse in Davenport. Spence was the only witness for the defense of Jerry Burns, who is charged with Martinko’s murder. The rested its case. The trial will continue Monday. (Olivia Sun/Des Moines Register)

DAVENPORT — A forensic consultant testified Thursday there may be another explanation for how the DNA of Jerry Burns was found on 18-year-old Michelle Martinko’s clothing, besides that he was her killer.

Michael Spence, owner of Spence Forensic Resources in Las Cruces, N.M., said there was a “distinct possibility” Burns’ DNA was found on the back of Martinko’s dress and car gearshift could have happened through transfer — because DNA can be transferred through a handshake or touching an object and could be passed to another person.

Spence, also a hired defense expert for Cristhian Bahena Rivera, 24, who is accused of killing University of Iowa student Mollie Tibbetts in July 2018, said he would expect to find other DNA on Martinko’s clothing if she had gone to a choir banquet and the Westdale Mall the night she was killed, Dec. 19, 1979.

Burns, charged with first-degree murder, is accused of fatally stabbing Martinko in her parents’ car, which was parked behind J.C. Penney at Westdale Mall. Her body was found by police Dec. 20, 1979.

According to testimony last week, the teen was stabbed 29 times. The fatal stab wound was to the sternum, which penetrated her aorta, and she bled to death, a pathologist testified.

A public genealogy database, GEDmatch, helped authorities identify Burns as a match to the DNA found on the back of Martinko’s black dress and car gearshift. Burns, a Manchester resident, was arrested Dec. 19, 2018.

During testimony Monday, a DNA expert said fewer than one in 100 billion unrelated individuals would have the same genetic profile found on the dress.

Burns did not take the stand, and the defense rested after Spence’s testimony.

The prosecution likely will have a rebuttal witness Friday. Closing arguments may start Monday. The trial is being held in Scott County because of pretrial publicity in Linn County.

Spence, who reviewed Iowa Division of Criminal Investigation reports but did not do any lab work himself, said the work and reports conducted in 2003 and 2005 when the profile was developed was thorough. But he criticized the handling of Martinko’s clothing. The dress, scarf, pantyhose and underwear were “bundled” together. He said They should have been separated because even dry items can transfer DNA onto the other. Humans, he said, shed 2 million cells per minute, and skin cells could be transferred when touching a glass.

Spence said he also did not know if the DNA found was blood or from another bodily fluid such as sweat, mucus or saliva. The concentration of the DNA found on the dress was only 3 nanograms, which is smaller than a speck of dust. The majority of it was from Burns, but there could be a small amount of Martinko’s DNA mixed in.

He said the amount isn’t consistent with someone cutting himself.

During trial, police investigators testified they believed the suspect cut himself during the fatal stabbing and was wearing gloves.   

First Assistant Linn County Attorney Nick Maybanks, on cross-examination, asked if Spence had any facts to show that a secondary transfer from Burns to Martinko happened.

Spence said no. He wasn’t testifying to that.

Maybanks also asked what circumstances have been have been laid out to show that Burns’ DNA could have gotten on Martinko’s dress Dec. 19, 1979.

Spence said there wasn’t any. He admitted Burns said he had been to the mall but not that night.

Maybanks said what if a young girl, who was later killed, came into contact with numerous people and they may have hugged her, sat with her, shared food with her. Would their DNA be on her?

Spence said there is a possibility.

Maybanks asked what “if a person was on top of her — holding her down.”

Spence said it would be “shocking” if DNA wasn’t found, unless it was someone who did not shed skin cells.

Would it increase the chances if both were cut or there were several cuts, Maybanks asked. Spence agreed.

If someone cut himself inside a glove, wouldn’t it make sense the blood would pool in the glove, Maybanks said.

Spence agreed.

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