A southeast Ohio woman told authorities in a taped confession that her son accidentally strangled his estranged wife with a plastic zip tie before his parents helped him dump the body in a church septic tank two years ago.

Sandra Inman, 47, is serving prison time for her involvement in the death of 25-year-old Summer Inman. She told investigators in 2011 that she wanted to see her grandchildren more so she came up with the idea of forcing her daughter-in-law into the car in Logan so they could discuss the issue, according to a transcript of the interview unsealed Thursday.

Once Summer Inman was forced into the back seat, her wrists were bound with zip ties. Sandra Inman said her son, William "Will" Inman II, put a zip around his wife's neck and accidentally strangled her as she struggled. Sandra Inman said they couldn't find a knife or anything else in the car to cut off the zip.

"I know, I know positively, he didn't do it on purpose," Sandra Inman told investigators.

Afterward, Sandra Inman said it was her idea to dump the body in a septic tank behind a church before going elsewhere and vacuuming out the inside of the car. During the interview a week after the murder, she instructed investigators where they could find the body.

While the March 29, 2011, interview with Sandra Inman was continuing, officers at the church unbolted the septic tank lid and reported seeing Summer Inman's leg sticking out in the tank.

"It's the stupidest thing I ever thought of to do in my whole entire life," Sandra Inman told investigators.

Sandra Inman pleaded guilty to murder and other charges last summer and was sentenced to 15 years to life in prison. Her husband, William Inman, 48, was sentenced to life in prison without parole after a jury convicted him last month.

William Inman II, was convicted last year and also sentenced to life in prison without parole.