Updated

Defense attorneys are trying to discredit a key prosecution witness who they say changed her story when it became clear she would be able to spare her own life by detailing the events that led to the shooting deaths of an Oklahoma couple.

Casslyn Welch, the cousin and girlfriend of defendant John McCluskey, took the stand for a third day Wednesday as the defense tried to establish a pattern of inconsistency.

McCluskey is facing federal carjacking and murder charges in the Aug. 2, 2010 deaths of Gary and Linda Haas of Tecumseh, Okla. If convicted, he faces either life in prison or the death penalty.

The Haases' bodies were found incinerated in their burned-out travel trailer on a remote ranch in eastern New Mexico. The slayings happened three days after Welch said she helped McCluskey and two other inmates escape from a privately-run, medium security prison near Kingman. One of the inmates was caught a day later in Colorado, but Welch, McCluskey and his former prison bunkmate Tracy Province sparked a nationwide manhunt.

Attorney Gary Mitchell pointed to Welch's testimony, saying it didn't match what she told investigators in the days following her arrest. He said it was Welch who initially took credit for targeting the couple and the idea to burn their travel trailer — with their bodies inside — to get rid of evidence.

It was also Welch, he said, who smuggled heroin and marijuana into two Arizona prisons so McCluskey could sell to his fellow inmates and eventually bankroll his escape.

"It wasn't done without you being involved," Mitchell told Welch.

Prosecutor Greg Fouratt said Welch admitted earlier this summer that she lied under oath about the extent of the drug smuggling operation. The summary of what happened when the victims were carjacked and killed remained unchanged, he said.

Welch is expected to finish testifying when the trial resumes Thursday.

Despite hours of cross-examination, Mitchell did not challenge Welch's statements that McCluskey was the triggerman.

Welch pleaded guilty last year to carjacking resulting in death, conspiracy, use of a firearm during a violent crime and other counts. She faces up to life in prison.

After getting choked up, Welch reiterated Wednesday that taking responsibility for her role in the carjacking and slayings was "the right thing to do."

Welch said the plan was to target someone with a truck and travel trailer so she, McCluskey and his former prison bunkmate Tracy Province could "get off the grid" and keep ahead of law enforcement agents. The plan didn't involve killing the Haases, but rather tying them up and leaving them in a remote area, she said.

To counter Welch's measured testimony, Mitchell played portions of the taped interviews in which she showed no remorse and spoke only of her disappointment that the trio would have to destroy the trailer, ditch the stolen truck and go back to using their cramped car.

As for the smuggling, Welch said she would use color-coded balloons to sneak heroin and marijuana in to McCluskey on a weekly basis. The account conflicted with statements she previously made to prosecutors.

Mitchell asked her again about lying.

"I've been protecting people all along, yes sir. That's why I lied," she said, later explaining she was afraid of what would happen to McCluskey in prison if she revealed details of the smuggling.

Welch said McCluskey was in charge of the operation in which he provided drugs to inmates, and their relatives or friends made payments to Welch. She also said she had drug customers outside the prisons.

At first, the extra money helped pay bills but then it became a way to bankroll the escape, she said.