BUTLER, Pa.—A New Jersey landscaper pleaded no-contest Tuesday in the deaths of his father and stepmother, killings Pennsylvania authorities said he sought to cover up with a story about a fake car crash even as he was trying to cash in on a multi-million dollar estate.

Colin Abbott, 42, of Randolph, N.J. entered no-contest pleas to third-degree murder in the 2011 deaths of pharmaceutical executive Kenneth Abbott and his wife, Celeste, at their western Pennsylvania home. The deal allows him to avoid the death penalty.

Authorities say Colin Abbott dismembered the bodies and scattered their charred remains on the family property in Butler County, about 50 miles north of Pittsburgh. Abbott then claimed they had perished in a fiery New Jersey car crash—a ruse that prompted the stepmother's family to post an obituary in her hometown newspaper.

Authorities had suggested Colin Abbott sought to inherit the bulk of his father's estate.

A Pennsylvania State Police complaint said Colin Abbott accompanied his father to the First National Bank in Slippery Rock to retrieve a safe deposit box on June 6. An employee of that bank signed as a witness to the changes Kenneth Abbott made to his will the previous month, according to estate records.

Police believe Abbott killed his father and stepmother shortly after the bank visit because by June 8 or 9, 2011, he was telling Celeste Abbott's relatives about a bogus car crash involving the couple.

But after a family member asked about a death certificate for insurance purposes, Colin Abbott became evasive. A distraught family member called the New Jersey State Police to ask about the remains, and they determined there was no record of any such accident or deaths.

Colin Abbott is scheduled to be sentenced Wednesday. Prosecutors are recommending a sentence of 35 to 80 years in prison.