A former Pittsfield man made his first appearance in court Monday on child sexual assault charges alleged by a family member to have taken place when she was under the age of 10.

William Heiser, age 61, of Lewiston was arrested at his home on a warrant at about 7 p.m. Thursday, Somerset County Sheriff Dale Lancaster said Monday.

The charges are gross sexual assault, a Class A felony, and unlawful sexual contact, a Class B crime. Detective Jeremy Leal of the Somerset County Sheriff’s Office Criminal Division was assigned to the case in February on a referral from the Vermont Department of Health and Human Services.

The alleged victim, now 16, made the allegations to a school mental health worker in Vermont where she now lives, Lancaster said.

“The girl would have been under the age of 10,” Lancaster said by phone Monday afternoon. “These are extremely serious charges. These are significant charges, and the severity of these crimes do not minimize over time. These crimes have a lifetime emotional and physical impact on the victims.”

Lancaster said the alleged assaults reportedly took place from 2009 until 2012 in the town of Pittsfield. Detective Leal worked the case with the Chittenden County Unit for Special Investigations in Burlington, Vermont, which provided a forensic specialist who interviewed the girl and obtained a full disclosure, he said.

The investigation into the allegations led Leal to Lewiston, where Heiser was living. Leal, working with the Lewiston Police Department Detective Division, located and interviewed Heiser. During the interview, Heiser confessed to the alleged assaults, according to Lancaster. After the interview a warrant was granted by the court, and on May 12 the Lewiston Police Department arrested Heiser at his home. Heiser was taken to the Somerset County Jail in East Madison the following day.

Lancaster said that his office is working with the Somerset County District Attorney’s Office and that the case is being reviewed for prosecution and potentially additional charges. Heiser was arraigned at the Somerset County District Court on Monday. He is being held on $250,000 cash bail, with stipulations that Heiser have no contact with the victim and no child under the age of 16.

Doug Harlow — 612-2367

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Twitter:@Doug_Harlow