MODESTO, Calif. -- Scott Peterson's former attorney says he has some powerful evidence that will help defend Peterson against charges that he murdered his wife, Laci, and his unborn son.

Scott Peterson's original attorney, Kirk McAllister (pictured left) said his office has uncovered evidence that will exonerate Peterson -- evidence that will be turned over to his new attorney. Defense sources say the new attorney will be Mark Garagos, NBC11's Karen Brown reported. 

McAllister told NBC11 that the defense's case is "strong." When asked why, he said, "because we investigated it instead of calling press conferences like the police did."

The key to Peterson's defense will be the testimony of witnesses uncovered by McAllister, witnesses he says need to be protected, Brown reported.

"I'm protecting witnesses, because I have concerns for them if I go public," he said.

According to defense sources, Los Angeles attorney Mark Garagos -- who has represented high-profile clients like Winona Ryder -- will take over the case Friday morning.

The current public defender says getting Garagos will only strengthen Peterson's defense.

"I think he's going to do a great job," said Kent Faulkner, the deputy public defender. "He's got the resources. He's got the knowledge. He's got the connections. I think it'll change the landscape of the way the case is tried."

Meanwhile, the District Attorney's office issued a statement saying, "We treat all cases as the case needs to be treated. Who the defense attorney is, is not going to change what we do."

In the meantime, Laci Peterson's family is busy preparing for the memorial that will take place Sunday at the First Baptist Church in Modesto.

Scott Peterson has not made an official request to attend that memorial, but the sheriff here says if that request is made, he'll deny it, Brown reported.