Tammy Anderson, 57, felt unnerved as four Indiana State Police troopers arrived at her apartment on Tuesday to arrest her husband, who never liked to talk much about his past.

Ms. Anderson’s husband, Ronald J. Anderson, 61, of Seymour, Ind., was being charged with murder, the troopers said, in connection with the 1982 killing of Clifford Smith, 24, who was Mr. Anderson’s brother-in-law.

As the troopers took her husband away in handcuffs, Ms. Anderson said in an interview on Wednesday, she felt indignant.

“I don’t know anything about this,” Ms. Anderson said, though she emphasized that she believed her husband was innocent.

Relatives of Mr. Smith said in interviews that they had long accused Mr. Anderson of being the culprit, even as an exact motive remained unclear for decades. The arrest, exactly 41 years after Mr. Smith was fatally shot in the head on Halloween in 1982 in Jackson County, in southern Indiana, has again raised tensions among the Smith family and Mr. Anderson’s relatives in a cold case that has long brewed bitterness and suspicion.

The arrest has also supported a secret belief that had festered for more than four decades within the Smith siblings’ households: A brother-in-law known for having a hot temper and taking psychedelic drugs had killed their shaggy-haired relative, they believed, and no detective could turn that inkling into an arrest warrant.