Prosecutor James Glasgow made the allegation at a bail reduction hearing for Peterson's $20 million bond.
Judge Carla J. Alessio-Policandriotes refused to reduce the bond for the suburban Chicago police officer, who is charged with first-degree murder in Kathleen Savio's 2004 death.
Peterson also is a suspect in the 2007 disappearance of his fourth wife, Stacy Peterson. He has maintained his innocence in Savio's death and Stacy Peterson's disappearance.
Glasgow said Peterson told a fellow police officer in late 2003 that he would be financially ruined by a pending divorce, and his life would be easier "if she was just dead." Glasgow did not reveal the source of his allegation.
Peterson attorney Joel Brodsky said that he had heard talk about Peterson trying to hire someone to kill Savio, but said it was "nothing substantive." He added that they would investigate Glasgow's allegations.
Former prosecutor Beth Karas, a correspondent for "In Session" on truTV, told Early Show Saturday Edition co-anchor Chris Wragge an allegation of this nature "is difficult to defend, but it's not impossible. (Actor) Robert Blake, of 'Baretta' fame, had two former stuntmen come forward to say he tried to solicit them to kill his wife, and the jury didn't believe them. He was acquitted of murder. So, it's something the defense has to deal with, but it's not an impossible hurdle."
Savio's body was found with a gash on the back of her head in her bathtub three weeks later, the Will County prosecutor said.
Peterson is a flight risk, he said, because he knows how to disappear and knows he faces 20 to 60 years in jail if he's convicted.
Brodsky said he wanted the judge to reduce his client's bond to under $1 million. He said Peterson has not fled, despite trips to Mexico, California and Florida, since police named him a suspect in Stacy Peterson's disappearance in late 2007.
Peterson, who is known for making smart-aleck remarks in the media, was much more subdued in court Friday. He hung his head as he left the hearing, and got into a van to go back to jail.
The former Bolingbrook sergeant finally understood the seriousness of his situation, Glasgow said.
Peterson "realizes there is no way out," he said.