In Wednesday's 5-2 decision, the high court said Wisconsin law makes sex acts with dead people illegal because they are unable to give consent.
The ruling reinstates the attempted sexual assault charges against twin brothers Nicholas and Alexander Grunke and Dustin Radke, all 22. The charges carry a punishment of up to 10 years in prison.
Justice Patience Roggensack, writing a majority opinion with three other justices, said state law bans sexual intercourse with anyone who does not give consent "whether a victim is dead or alive at the time."
"A reasonably well-informed person would understand the statute to prohibit sexual intercourse with a dead person," she wrote.
Jefren Olsen, an attorney who represented Radke, said the decision was flawed because the law was never intended to punish necrophilia.
"Obviously, the facts are rather notorious and not the easiest to deal with," he said. "I assume that had some impact."
Police say the three men, carrying shovels, a crowbar and a box of condoms, went to a cemetery in southwestern Wisconsin in 2006 to dig up the body of Laura Tennessen, 20, who had been killed the week before in a motorcycle crash.
Nicholas Grunke had seen an obituary photo of her and asked the others for help digging up her corpse so he could have sexual intercourse with it, prosecutors say.
Authorities say the men used shovels to reach her grave but were unable to pry open the vault. They fled when a car drove into the cemetery and were eventually arrested.
The men were charged with attempted third-degree sexual assault and misdemeanor attempted theft charges. The case has been on hold as prosecutors appealed the dismissal of the assault charges.
Suzanne Edwards, a lawyer representing Nicholas Grunke, said she was disappointed in the decision. She said the men will be arraigned on the charges and have a chance to plead not guilty.
Attorney General J.B. Van Hollen, whose office represented prosecutors in the appeal, praised the decision.
"Words matter and the Legislature chose its words carefully to extend the sexual assault law to those heinous circumstances where a dead person is sexually assaulted, whether or not the defendant killed the victim," he said. "Necrophilia is criminal in Wisconsin."
The decision brings Wisconsin into line with more than 20 other states that prohibit necrophilia or the abuse of a corpse, according to the National Conference of State Legislatures. California joined the group in 2004 after prosecutors said they couldn't bring charges in some cases without an official ban.
The law in Wisconsin had been murky, and two dissenting justices insisted Wednesday that lawmakers did not mean to ban necrophilia but to allow assault charges when someone was raped and then killed.
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