Several dozen spots of suspected blood were marked by forensic scientists combing Jeffery Trevino and Kira Steger's St. Paul home for possible signs of a murder, but not all the samples were thoroughly tested to determine their makeup and origin, scientists testified Tuesday.

The difference in how some suspected blood evidence was treated compared with others stoked the most tension yet between Ramsey County prosecutors who are trying to prove that Trevino killed his wife in a jealous rage and defense attorney John Conard, who at one point handed a textbook to a scientist on the witness stand when she couldn't answer his question.

"You want to give that a read?" Conard asked Lindsey Garfield, a scientist at the Minnesota Bureau of Criminal Apprehension.

Trevino, 39, faces two counts of second-degree murder in Ramsey County District Court in the death of Steger, 30, who was last seen alive on Feb. 21 and whose body was recovered on May 8 from the Mississippi River.

Conard has long waited to pounce on the forensic evidence prosecutors are levying against his client. Prosecutors wrongly describe the residence as containing "copious amounts" of blood evidence, Conard has said, when "less than a thimble" of Steger's blood was found there.

Garfield's statements came during the longest testimony of the 36 witnesses who have spoken so far. She took the witness stand for nearly six hours on Tuesday, the fourth day of testimony.

Garfield processed much of the alleged blood evidence recovered Feb. 25 and 26 from Trevino and Steger's rental home in the 500 block of Iowa Avenue E., and tested several locations with "presumptive" tests. Several spots identified in the master bedroom, hall, kitchen and bathroom tested positive for blood with the presumptive tests, which are not definitive without further testing, she testified.

Garfield said many of the spots were visible to the naked eye and were dark-colored, while others only showed up after the chemical luminol was applied to surfaces in the home. The chemical glows a neon blue in the dark when it comes into contact with blood, metal and other substances.

A second test using phenolphthalein was used to determine the presence of blood, she said. A third test, Hematrace, was used minimally. All three are preliminary tests performed on-site.

The problem, Conard pointed out, is that luminol and phenolphthalein are "extraordinarily sensitive" and react to a number of substances, including old stains. Hematrace reacts positively to ferrets, he said. Phenolphthalein reacts positively to horseradish, he said.

Garfield agreed on all points, and testified that more than a dozen spots that tested positive at the scene for presumptive blood were not submitted for further lab testing at BCA headquarters. Several of the spots were on the carpet between the master bed and closet doors, where much of the alleged blood spatter was found.

It's unclear whether there are more unverified presumptive results, but Conard walked Garfield through more than a dozen.

"As a matter of science, it would be wrong to establish that we have blood here without further testing?" asked Conard.

"We have a presumptive positive and that's as far as I can go with that," Garfield said.

Garfield testified that one spot on a wall tested positive for presumptive blood with phenolphthalein, but later tested negative for human blood.

Phenolphthalein does not differentiate between human and nonhuman blood.

Steger had a small dog in the home.

At one point, when Garfield could not answer a question about blood volume and dripping, Conard handed her a textbook.

"I haven't committed the book to memory," Garfield said.

Prosecutors said that several spots underwent further testing and that a BCA DNA scientist will testify about those results Wednesday. The exact number was not disclosed.

Garfield said that suspected blood was found on a box spring, bedroom baseboard, bedroom carpeting and the bedroom door under the knob. The red-brown smear under the door knob also appeared to have a possible fingerprint, Garfield said.

Preliminary tests showed positive blood results for spots in Trevino's Honda CR-V, a towel recovered from inside his car, several locations on Steger's car — including in the trunk — and on a pillow found in a plastic bag at Keller Lake on March 16, Garfield testified.

Tuesday' testimony began with Steger's grandfather, Norman Kelch, who discovered the plastic bag at Keller Lake. Authorities have said Steger's DNA was found on the evidence.

Kelch, who traveled to Minnesota from his home in Louisiana to search for his granddaughter, said he spotted a white Wal-Mart bag in a snowy ditch. It looked unusual, so he retrieved it and ripped it open. Shadows hindered his sight, so he carried it to a sunny location and ripped a bigger hole.

"I seen bloody objects in the bag," he said as a few of Steger's family members dabbed the corners of their eyes. "A bloody cloth … I just backed up from there."

Testimony will continue on Wednesday.

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