BARNSTABLE, Mass. -- On the stand Thursday, the jury heard from a forensic scientist who blasted the way evidence in the Christa Worthington murder investigation was collected at the crime scene.

Trash collector Christopher McCowen is accused of killing the fashion writer.

NewsCenter 5's Amalia Barreda reported that the jury also heard the words of Worthington's daughter, Ava, who desperately tried to help her mortally injured mother.

"Do you recall reviewing a report with a direct quote from Ava, 'Mommy won't get up. Tried to get mommy up. Mommy dirty. Tried to clean mommy'?" prosecutor Robert Welch asked a defense forensic expert.

It was the first time Ava's words after her mother's murder had ever been revealed. The 2 ½-year-old was found clinging to her mother's dead body.

A forensics expert for the defense stood by his claims Thursday that the State Police Crime Lab made some serious mistakes in the case, beginnning with the failure to do DNA testing on bodily fluids found on Worthington's body.

"So, we have a big question mark here, obviously. And it's a question mark that could have readily been solved with the analysis of that one specimen," said forensic scientist Dr. Richard Saferstein.

Several bloody areas and items found around the victim's house, such as a heavily bloodstained wash towel, also were not tested.

"So this is also a good piece of evidence to see if there is a perpetrator's DNA would have been present on that mitt," said Saterstein.

It was the same story with hairs and fibers, including blue and white fibers found on Worthington's body. Jeremy Frazier, the man McCowen said killed Worthington, was wearing a blue and white sweater that night that he was turned over to police.

"What type of testing was done on it?" Welch asked.

"Nothing," Saferstein said.

Earlier in the day, Worthington's cousin, Pamela, told the defense that she couldn't remember comments she made to police after the murder.

"That Christa would entertain a possible relationship with any type of man, irregardless of status, looks, personality or marriage status?" defense attorney Robert George asked.

"I do not remember saying that," Pamela Worthington Franklin said.

The last witness for the defense on Thursday was a forensic psychologist who told the jury McCowen's low IQ made him susceptible to manipulation during his long and stressful interrogation by police. That testimony intended to bolster the defense theory that McCowen was bullied into admitting he committed the crimes he is charged with.

Testimony in the Cape Cod murder case could finish up as soon as Friday.