Marty Grismer is currently in prison at Montana State Prison in Deer Lodge, Montana. In 2018, he was sentenced to 100 years for shooting his ex-girlfriend, Kari Sweeney, to death in October 2016 at her home in Bozeman. Kari, a 38-year-old mother of three, was killed after she ended their relationship. Marty, then 62, admitted to the crime after turning himself in two days later.
The case showed a history of arguments between them, and Marty Grismer pleaded guilty to deliberate homicide in a plea deal. He won’t be eligible for parole until 2043 when he’d be 88. The Dateline NBC episode about his case, “The Ranch,” aired on March 14, 2025, at 9 p.m. ET on NBC. Reported by Keith Morrison, it was released across the U.S. and streamed on Peacock the next day.
Who was Kari Sweeney, and what was her relationship with Marty Grismer?
Kari Sweeney was born on April 12, 1978, in Bozeman, Montana, to parents Lyle and Carol Sweeney. She grew up in Bozeman with two sisters and loved the outdoors, especially skiing and hiking. Kari went to Bozeman High School and graduated in 1996. She then studied at Montana State University, earning a degree in psychology in 2000. After college, she worked as a dental hygienist in Bozeman. Kari was known for being kind and raising her three kids—two daughters and a son.
Kari met Marty Grismer around 2005 when they were both in their late 20s. They dated for years and lived together in Bozeman. Their relationship had ups and downs, with fights over money and Marty’s drinking. Kari ended things in July 2016 because of his behavior, asking him to move out of her house.
Everything to know about Marty Grismer
Marty Grismer, who was born in 1955 in Bozeman, Montana, shot his former girlfriend Kari Sweeney to death in October of 2016. Kari, 38, a mother of three dental hygienists, had cut off their year-long relationship with Marty in July 2016 due to drinking and fights. They had dated since 2005 and were living together,r but she told him to move out of her home on Bridger Canyon Road in Bozeman.
In his 20s, Marty got interested in outdoor activities like hunting and fishing, which he enjoyed with friends. He never married or had kids but lived with his dog, a German Shepherd named Rusty, for many years. By his 50s, he was known as a quiet guy who kept to himself, living in a small house near downtown Bozeman. He worked odd jobs to pay his bills and spent time fixing up old cars as a hobby. Marty stayed close to his hometown his whole life.
Where is Marty Grismer Now?
According to NBC, Marty Grismer killed his ex-girlfriend Kari Sweeney in October 2016. Kari, a 38-year-old dental hygienist and mother of three, had ended their long relationship in July 2016 because of Marty’s drinking and arguments. They had dated since 2005 and lived together, but she asked him to leave her home on Bridger Canyon Road in Bozeman.
On October 12, 2016, around 10 p.m., Marty went to Kari’s house after drinking at a bar. He broke in through a window, found Kari asleep in her bedroom, and shot her three times in the head with a .38-caliber revolver he owned. Her 14-year-old son was home but didn’t hear the shots because he had headphones on. The following day, the corpse of Kari was discovered by her sister as she could not be awakened by her children. Marty had escaped and discarded the gun in a river.
Two days later, on October 14, Marty turned himself in at the Gallatin County Sheriff’s Office, saying he “did something bad.” Police found Kari’s blood on his shoes and linked the bullets to his gun, which divers recovered from the Yellowstone River. The investigation showed Marty was upset about the breakup and had been drinking heavily that night. Text messages from Kari’s phone proved she had cut ties with him months earlier.
In December 2018, Marty had pleaded guilty to deliberate homicide under a plea agreement to avoid trial. On March 12, 2019, Judge John Brown imposed 100 years at Montana State Prison with no parole until 2043. Kari’s family spoke at the sentencing, asking for a long sentence. Marty is now 70 and still in prison in Deer Lodge, Montana.
Read More: Ahead of Dateline on NBC: The Truth About Husbands of Lori Vallow
Follow us on Instagram and Twitter.
Hilfa, Senior Writer at Hilvaro, excels in pop culture journalism. She crafts engaging content on movies, TV, & trends, fueled by her love for storytelling & entertainment.
Discover more from Hilvaro
Subscribe to get the latest posts sent to your email.
One thought on “Where is Marty Grismer Now? NBC’s Dateline Explores Marty’s Case”