Updated

The husband of a Missouri woman who has been missing for nearly a year was charged with first-degree murder Monday even though his wife's body has not been found.

Clay Waller, 41, also was charged with tampering with evidence in the death of his estranged wife, Jacque Waller, who was 39 when she disappeared June 1.

Clay Waller already is in federal prison for threatening his wife's sister, who has been caring for the couple's 5-year-old triplets since their mother's disappearance. He does not have a listed attorney.

"There is a bit of relief in knowing that charges have been brought against Clay Waller," Jacque Waller's father, Stan Rawson, said in a statement. "The case is now in the hands of the prosecuting attorney, and we are confident that we will now finally get justice for our girl."

The Wallers had been having marital trouble and were on the verge of a divorce last June, Rawson told The Associated Press last year. They used the same attorney and met with him on the day Jacque Waller disappeared. Jacque Waller's sister, Cheryl Brennecke, became suspicious that day when she couldn't reach her sister. Rawson said Jacque Waller had previously confided to her sister that Clay Waller had threatened her.

Jacque Waller's car was found near Fruitland along Interstate 55 the day after she went missing. Several searches since then have turned up sporadic leads, including the discovery of her purse in November near the site where the car was found.

The FBI said last year that Clay Waller suggested to his father that he had broken Jacque Waller's neck and buried her in a hole that he dug in advance. But Clay Waller has not made any confession to police, and his father died before he could testify.

Waller was sentenced to five years in federal prison in December and is serving time at a prison in the state of Louisiana. He pleaded guilty in October to threatening Brennecke through an online posting.

"This is just the first part of it," Cheryl Brenneke, Jacque's sister, told the Southeast Missourian newspaper. "We will not rest until there's justice for Jacque, that's for sure. We won't let him get by with this. We're going to win this for her."

Cape Girardeau County prosecutor Morley Swingle said one of the tampering charges alleges Clay Waller concealed his wife's body. The second alleges he "concealed bloodstained carpet from the hallway of his home" in Jackson, Mo., about 100 miles south of St. Louis.

Swingle said Missouri lets prosecutors seek the death penalty if at least one of 17 "aggravating factors" can be proven. He said none of the aggravating factors are involved in the Waller case.

The Associated Press contributed to this report.