The way to do it and get away with it, Mr. Higgs is said to have told another nurse, is with an injection of the paralytic drug succinylcholine because it frequently goes undetected in autopsies.

That alleged conversation - and a laboratory test that turned up succinylcholine in the body of Mr. Higgs's wife, Kathy Augustine - formed the basis of the indictment. Now, the investigation into the death of Ms. Augustine has prompted the authorities to look into another death three years ago, that of her first husband, Charles Augustine, 63, who died in a Las Vegas hospital where he was being cared for by Mr. Higgs.

David Roger, the district attorney for Clark County, announced Monday that investigators would exhume Mr. Augustine's body to check for traces of the same drug that officials say killed Ms. Augustine.

Mr. Higgs, who was arrested on Friday in Hampton, Va., where he was staying with relatives, waived extradition on Monday and will be returned to Nevada. He has not made any public remarks since an impassioned denial of wrongdoing in an interview with The Las Vegas Review-Journal on July 13, in which he insisted he loved his wife and called suspicion of his involvement "just crazy."

The day after those remarks, Mr. Higgs was found with his wrists slit in the Las Vegas home he and Ms. Augustine had shared. He was treated at a local hospital and released but did not attend his wife's funeral on July 15.

The death of Ms. Augustine, 50, who was the Nevada state controller, and the case's potboiler-style twists have captivated Nevadans.

According to police reports, Mr. Higgs called the police the morning of July 8 and said he had found his wife unresponsive and not breathing at their second home in Reno. He suggested to paramedics that she might have had a complication from a heart condition.

Ms. Augustine died three days later, and an autopsy by the Reno coroner found no evidence of heart disease or heart attack.

With no visible explanation for the death, Ms. Augustine's blood samples were sent to the F.B.I. laboratory in Quantico, Va. Last week, the lab reported the presence of succinylcholine, and Ms. Augustine's death was ruled a homicide. On Friday, Mr. Higgs, 42, was arrested on one count of first-degree murder.

"It's a major punch in the gut to the family," Greg Augustine, 36, son of Charles Augustine and stepson of Kathy Augustine, said Saturday. "We were holding out hope that there wasn't any foul play. Now we know she was killed."

Now that Mr. Higgs has been accused in this death, questions have arisen about the death of Charles Augustine.

"My dad was getting better, and they were moving him to a rehab area," Greg Augustine said in July, "but very soon after that, he had massive organ failure."

No criminal investigation was conducted at the time of Mr. Augustine's death.

Mr. Higgs and Ms. Augustine were married three weeks after the death of Mr. Augustine in 2003, and the newlyweds received $1 million from his life insurance policy.

Greg Augustine said his father and stepmother were in the midst of a divorce after 17 years of marriage when the elder Mr. Augustine was hospitalized. Greg Augustine said he had had little contact with his stepmother after his father's death but does not suspect she was involved in his father's death.

The indictment against Mr. Higgs says he injected succinylcholine into Ms. Augustine's buttocks on July 8 before calling the police. Succinylcholine is a muscle relaxant used by anesthesiologists to briefly paralyze patients in order to install breathing tubes, but it has also been used as a murder weapon. Efren Saldivar, a respiratory therapist, confessed in 2001 that he injected it into some of his more than 50 victims in California.

The indictment against Mr. Higgs said he had mentioned his marital discord as well as the use of succinylcholine to a fellow nurse at the Reno-area hospital on July 7. The two were discussing a high-profile arrest of a man charged with gunning down his wife, and Mr. Higgs reportedly remarked that such a means of killing someone was "stupid." The nurse, not named in the indictment, informed the police of the conversation as Ms. Augustine lay comatose before her death three days after her collapse.