Olathe ? A former school custodian who was convicted last year of killing a Prairie Village girl 30 years ago has been sentenced to life in prison, with no chance of parole for 15 years.

In Johnson County District Court on Thursday, John Henry Horton, 57, continued to insist that he was not guilty of the crime, but he also apologized to the family of Lizabeth Wilson for what they had been through.

The girl was 13 when she disappeared on July 7, 1974. She last was seen in a parking lot behind Shawnee Mission East High School after she left the Prairie Village municipal pool. She was only a few blocks from her home and not far from the police department.

Her skeletal remains were found six months later in a Lenexa field that was being cleared for construction.

Horton was found guilty of first-degree felony murder by a jury in September. Prosecutors said Lizabeth died after Horton used chloroform to knock her out so he could sexually assault her.

Horton, 27 at the time, was working as a custodian at the high school the day Lizabeth was killed. He was considered a suspect at the time, and authorities found several bottles containing chloroform when they searched his car.

Horton told officers he took the items from the school that day because he wanted to “get high.”

Family members had been afraid Lizabeth’s killer would never be brought to justice, but a 44-year-old woman came forward in 2002 with a story of sexual molestation that linked Horton to the slaying.

John Henry Horton, right, stands in court for sentencing Thursday at the Johnson County Courthouse in Olathe. Horton was found guilty of the 1974 first-degree murder of Lizabeth Wilson. He was sentenced to life in prison. Horton's attorney, Michael McCulloch, is at left.

The woman, who had lived across the street from Horton in 1974, told investigators about an excursion with Horton to a golf course that summer, when she was 14. She said Horton opened a brown bottle of foul-smelling liquid, poured some on a rag and held it to her mouth, causing her to pass out.

The woman testified in court that when she awoke, Horton was molesting her. She said she became violently ill and went home after the incident.

She never talked to Horton again, and she never told anyone else what had happened to her.

“There is no question she made the difference,” said assistant prosecutor Rick Guinn.

In October 2003, officers went to Horton’s home in eastern Missouri and knocked on the door. Horton jumped out a rear window and made a run for the woods when his wife opened the door, but a local deputy chased him down. He has been in custody ever since.