The firing of a longtime Tisbury police sergeant over his alleged mishandling of a 2011 domestic and sexual assault case was upheld last week by an arbitrator.

In a decision dated Oct. 12, arbitrator Richard G. Boulanger found that the selectmen’s November 2011 decision to dismiss Sgt. Robert Fiske was justified.

Sergeant Fiske, who had been with the department for 20 years, was fired for failing to comply with the Tisbury police department’s domestic violence and sexual assault policies.

In a press release issued late last week, the town said the sergeant’s “actions and inactions” in responding to the July 2011 incident led to his dismissal.

“Your actions that night were not in keeping with the standards of performance expected of a sergeant and senior member of the Tisbury police department and were in direct contravention of clear and unambiguous department policies,” the town said in its November 2011 decision.

On July 23, 2011, Tisbury police, including Sergeant Fiske, were called to the West Spring street home of David Thrift and his wife, after receiving a call from his wife that Mr. Thrift was physically assaulting her after she had found him assaulting a 15-year-old relative. When police officers arrived, Mr. Thrift fled.

According to the arbitrator’s decision and the police report, Mr. Thrift’s wife was taken to the hospital and Sergeant Fiske and other police officers searched for Mr. Thrift and returned to the police station. Meanwhile, Mr. Thrift returned to the home and raped the 15-year-old, who had stayed to watch the couple’s three young children.

Sergeant Fiske and other police officers returned to the home and arrested Mr. Thrift.

Four months later Mr. Fiske was fired following an internal investigation by the town.

The criminal case against Mr. Thrift concluded two weeks ago in Dukes County superior court, where he pleaded guilty to rape of a child by force, rape of a child under 16, intimidation of a witness, assault and battery, violating an abuse prevention order, and two counts of solicitation of a felony. He was sentenced to 10 to 13 years in state prison.

And late last week Sergeant Fiske’s appeal of his termination also ended with the ruling from the arbitrator. “The decision to terminate Mr. Fiske was a difficult one, but the board felt compelled to do so, given all the circumstances,” the selectmen said in a statement. “While the board takes no pleasure in the circumstances surrounding Sergeant Fiske’s termination, it is gratified that a neutral, independent party has concluded that the board’s decision was justified, after a review of all the evidence.”

Sergeant Fiske’s grievance was aired at two hearings in May at town hall and one hearing in June at the Department of Public Works, according to the arbitrator’s decision provided to the Gazette.

The town said Sergeant Fiske failed to implement policies that he helped to co-author, while the union said he acted appropriately based on his experience and training.

The town said it had cause to terminate the sergeant because he failed to secure the crime scene where Mr. Thrift assaulted the 15-year-old, did not provide emergency medical care and “devoted little attention to” the teenager during his time at the house.

The town also pointed out the failure to provide police protection to the teenager and the Thrifts’ three children when they were left alone at the home. Department domestic violence policies call for police to remain on the scene as long as the officer has reason to believe that any of the parties are believed to be in danger.

“On July 23-24, 2011, the grievant’s performance was subpar by any measure. His misconduct reveals his inability to perform as a town police officer. His failure to accept responsibility for his misconduct . . . makes a lesser penalty, such as a suspension or a demotion, unworkable,” the town said.

The union contended that Mr. Fiske “acted reasonably based on the information that he received [at the home] upon his arrival and during his stay.”

The union said the events were unforeseeable and that department policies did not specify behavior but served as guidelines. It called the suggestion that Sergeant Fiske should have assigned an officer to stay “hindsight analysis,” and said termination was too severe a penalty, noting Sergeant Fiske’s long service to the town and the fact that the chief continued to assign him cases after the incident, including accompanying the teenaged victim and Mr. Thrift’s wife to off-Island counseling.

“The town’s investigation into the incident was flawed. It is clear that the findings and conclusions of the investigation were pre-ordained with the goal of terminating the grievant,” the union said, according to the arbitration document.

“The grievant can’t be faulted and disciplined for a tragic consequence that resulted despite his best efforts.”

But the arbitrator sided with the town, finding it had just cause to fire Sergeant Fiske because of his failure to follow domestic violence and sexual assault guidelines, which he helped to craft.

The chairman of the selectmen said the ruling closes a painful chapter for the town. “I’m glad this decision is behind us,” Tristan Israel told the Gazette Monday. “I feel bad for everybody involved.”