10/03/2012 03:00 pm ET

Kim Crespi Wants Husband David Crespi, Who Murdered Their Twin Daughters, Out Of Prison

A man pleaded guilty to stabbing his twin daughters to death six years ago, but the girls' mother says he doesn't belong in prison.

Kim Crespi told WBTV that when the murders of five-year-olds Tessara and Samantha took place in North Carolina, her husband, David Crespi, was psychotic due the to multiple prescription drugs for anxiety, insomnia and depression that he'd recently begun taking.

"It wouldn't have happened without the prescriptions," she told WSOCTV. "David Crespi never acted like this ever in his life."

Crespi was alone with the twins when he stabbed them, then called 911 to report the murder. The cocktail of drugs that his wife said pushed him over the edge was Prozac, Ambien, Trazadone and Lunesta. According to her website, he'd been taking the medications for one to three weeks.

The couple has three older children, and Kim Crespi lives with them in the Charlotte home the family once all shared. She visits her husband in prison every week or two, and says he is "back to his old self" after being off medication for several years, according to the Charlotte Observer.

David Crespi entered guilty plea came to avoid the death penalty, but it led to a life sentence with no chance of parole.

Though his wife has not filed any paperwork yet, she says she plans to hire an attorney to try to have the plea set aside. She wants her husband to have a new trial so that a jury can rule on whether or not his prescription drugs were responsible for the incident.

Kim Crespi told the Observer that the six years her husband has spent in prison is already too much. "He should not be punished," she said. "He didn't have free will at the time when he did this."

Next week, she is planning to host a public forum featuring David Carmichael, who murdered his 11-year-old son in 2004. Carmichael, who was on antidepressants at the time of the murder, was ruled "not criminally responsible on account of a mental disorder" by a Canadian judge in 2009. Now a free man, Carmichael writes and speaks on the dangers of antidepressants.

Crespi hopes that her story, combined with Carmichael's, will help educate others on the potential effects of medication.