LOCKPORT, NY (WIVB) The case went unsolved for decades, but on Thursday, Niagara County prosecutors began presenting their case against against Joseph Belstadt for the murder of Mandy Steingasser.

“The evidence will show that Mandy Steingasser rejected the defendant’s advances and he flew into a rage and he killed her,” said John Granchelli, assistant district attorney for Niagara County. Belstadt was 18 at the time. Steingasser was 17 years old on the day she disappeared, September 19, 1993.

What is not disputed is that Belstadt picked up Mandy Steingasser in his car that night in North Tonawanda and even asked his friends to lie about his whereabouts at that time. What a jury of 9 women and three men will have to decide is whether he killed her and left her body in Bond Lake Park in North Tonawanda.

“You will hear testimony that this defendant knew it was muddy when Mandy Steingasser was because he had taken another girl to a spot a couple dozen feet away from where Mandy Steingasser was found a week or two before Mandy went missing,” said Mary-Jean Bowman, assistant district attorney for Niagara County.

“You’ll see her body dumped in the woods, the same clothes she was last seen wearing September 19,1993,” said Granchelli. “Her pants ripped and unzipped, her underwear exposed, her skull fractured, her fingernail broken, her belt loop ripped off, buttons missing from her vest, her shoes missing, every hook torn from her bra and then tied around neck.”

But defense attorney Michele Bergevin argues that some of the forensic evidence found on her body trace back to other people, and none of the evidence found in his car prove he killed her. “The government will not be able to prove beyond a reasonable doubt that Joe Belstadt touched Mandy Steingasser, let alone intentionally murdered her.”

The trial is expected to last about six weeks. Between 65 and 80 witnesses are expected to testify. The first witness is scheduled to take the stand on Friday morning.