Nathan J. Carman, the Vermont man questioned in the 2013 murder of his wealthy grandfather, said in a related lawsuit that he refused a polygraph because the notion that he had to prove his innocence was “abhorrent to me,’’ records show.

The statements from ­Carman, 24, were contained in court filings made public Wednesday in a New Hampshire lawsuit brought by his aunts, who hope to block him from collecting millions of dollars from the estate of his grandfather, John Chakalos.

Chakalos was found shot to death in his Connecticut home in December 2013. The case remains unsolved, but police have described Carman as a person of interest and say he bought a gun that was the same caliber as the murder weapon. Carman’s firearm went missing, according to police.

As part of the aunts’ lawsuit, their lawyers put several written questions to Carman, including an inquiry regarding his refusal to take a polygraph exam during the murder probe.

Carman, in his written response, said he refused a lie detector “because the accuracy and reliability of polygraph results are questionable, and the principle of attempting to prove my innocence, a seeming waiver of one of the most fundamental human rights, the right to be presumed innocent until proven guilty, is abhorrent to me.’’

He also gave an account of his activities on the night of Chakalos’s murder. Authorities have said Carman was the last person to see his grandfather alive.

Carman wrote that he dined with Chakalos at a Greek restaurant on the evening of Dec. 19, 2013, and then drove his grandfather back to his Windsor, Conn., residence.

Carman said he spent a few minutes inside with Chakalos, before Chakalos took a call.

“We hugged at the door, and I left in my truck,’’ Carman wrote.

Carman said that he drove back to his apartment in Bloomfield, Conn., and stayed there until about midnight, when he left to buy ice cream at a grocery store. He returned home, he said, and lost track of time while playing a computer game. He then left late for a planned meeting with his mother, who was scheduled to go fishing with him.

Carman said he got off at the wrong exit and was delayed in getting to his mother, but the two eventually met and left for the trip around 6 a.m.

Investigators have said Carman discarded his computer hard drive and GPS unit on the morning after the killing.

Carman has also faced scrutiny for the disappearance of his mother, Linda Carman, during a second fishing trip in 2016. Nathan Carman’s boat sank about 100 miles offshore during that trip, and his mother vanished. Nathan was rescued several days later on a life boat.

The boat’s insurer has alleged in a separate lawsuit in Rhode Island that Nathan Carman made suspicious alterations to the vessel before the trip, with the intention of sinking the boat.

Carman has adamantly denied killing his grandfather or intentionally harming his mother. With his mother presumed dead, her share of Chakalos’s $44 million estate would eventually go to Carman, her only child.

In the questionnaire in the New Hampshire lawsuit, Carman wrote that he “did not receive a financial benefit as a result of my grandfather’s death.’’

Carman said his grandfather provided generous financial support to him , totaling more than $100,000 annually, which “ceased’’ after the murder.

“The loss of that financial support has more than offset the half of his Fidelity checking account balance ($200,000) that I received after his death,’’ Carman wrote.

He said that since Chakalos’s death, he’s become the administrator of a qualified tuition plan “of which I am the beneficiary.’’ The plan was funded with “approximately $160,000 before my grandfather’s death,’’ Carman wrote.

He also asserted his Fifth Amendment right against self-incrimination when his aunts’ lawyers requested documents related to his purchase and ownership of guns between January 2011 and Dec. 23, 2013, four days after the murder, legal filings show.

During a court hearing Monday in the New Hampshire suit, a lawyer for Carman’s aunts, Daniel Small, said the plaintiffs have asked Carman to produce the Sig Sauer rifle he bought that is the same caliber as the murder weapon, and Carman once again refused on Fifth Amendment grounds.

Carman insisted during the hearing that “I didn’t kill my grandfather,’’ and he’s suggested his aunts had a motive to carry out the slaying, a claim Small has derided as “nonsense.’’

Travis Andersen can be reached at travis.andersen@globe.com.