Drew Peterson's Attorney: Couple's Son Will Be Key Witness

Joel Brodsky, an attorney for Drew Peterson  -- the ex- police sergeant  from suburban Chicago, IL now charged with murdering his third wife  --  told the CBS Early Show Friday that one of the couple's boys has "provided a lock-tight alibi" for the former lawman.  

In a stunning move, Peterson -- who's been under a cloud of suspicion since October, 2007 when his fourth wife Stacy mysteriously disappeared -- was arrested Thursday.  He was immediately charged with killing his third wife Kathleen Savio and was ordered held on a staggering $20 million bond.

Peterson is slated to be arraigned Friday on first-degree murder charges, and could serve up to 60 years in prison if convicted.

Brodsky said Peterson will plead "not guilty to all charges, obviously."

Peterson, 55, is accused on orchestrating the 2004 drowning death  of Savio. At that time, her death was ruled an accident.   The case was re-opened after Peterson's fourth wife Stacy turned up missing more than three years later.  She has never been found.    

Brodsky told Early Show co-anchor Maggie Rodriguez that forensic evidence the defense will spotlight will vindicate his client of said charges, and show the death was accidental.

"We still believe that never has been, a homicide, that Kathy's death was accidental, and we believe that when we get our pathologist in and have him review everything, that ... that will be upheld, that, beyond a reasonable doubt, it was an accident," he said. "This is, at best, a weak circumstantial case."