Drew Peterson was convicted of murdering his third wife. (Will County Sheriff's Office)

As the Associated Press reports,

"The trial was the first of its kind in Illinois history, with prosecutors building their case largely on hearsay thanks to a new law, dubbed 'Drew's Law,' tailored to Peterson's case. That hearsay, prosecutors had said, would let his third and fourth wives 'speak from their graves' through family and friends to convict Peterson.

Hearsay is any information reported by a witness that is not based on the witness' direct knowledge. Defense attorneys said its use at the trial would be central to their appeal."

Peterson's fourth wife, Sandy, disappeared in 2007. This pushed authorities to take another look into the 2004 death of Peterson's third wife, Kathleen Savio, which was initially ruled an accident and re-classified as a homicide after the second investigation.

The state of Illinois passed a law in 2008 making evidence based on hearsay admissible in court under certain circumstances. This made it possible to try Peterson for the murder of Savio, a crime in which there was no physical evidence or eyewitnesses. Instead, prosecutors used testimony from friends of Peterson and the deceased women in which they recounted conversations that tied Peterson to Savio's murder.

While Savio's family expressed relief and vindication at the verdict, they acknowledged there was still unfinished business. Her brother, Nick, ended his remarks by saying "Stacy, you are next for justice."

Illinois does not have the death penalty, but Peterson faces a sentence that could top out at 60 years.

Reach Executive Producer Matt Pressberg here.