A Tisbury police officer returned to work Thursday just as the town released a report that harshly criticized his handling of a detainee who ended up in the emergency room after he had left her alone in his cruiser.

Det. Mark Santon, who has served on the town force for more than 25 years, had been on paid administrative leave since Jan. 31, while the town hired a retired Cape Cod police chief to examine his handling of the Jan. 27 incident.

His return coincides with a change in Tisbury police policy and procedure involving the transport of people who have been arrested to the county jail. The new policy will require that anyone arrested not be left alone for any period of time as they are transferred.

On Jan. 27, Mr. Santon responded to a minor accident involving two vehicles, one operated by Mark Clarke, 51, of Vineyard Haven, and the other operated by Alice A. Ribeiro, 41, of Edgartown, according to the publicly available police reports. When officers responded to the scene, a check revealed that she was a Brazilian national with no driver’s license and one prior arrest in 2009 for driving without a license. Reports recount that she was placed under arrest, handcuffed behind her back and placed in the back seat of a cruiser driven by Detective Santon for transport to the Dukes County jail in Edgartown.

Detective Santon’s report details the events upon his arrival at the jail. When he went inside seeking a deputy for assistance, he left Ms. Ribeiro in the back of the cruiser for what his report describes as “a few minutes.” According to the report, when the law enforcement officials returned to the car the woman was slumped over and unresponsive, apparently having freed one hand from the cuffs. The cord from the hood of her sweatshirt was “tightly wrapped around her neck twice and tied off with a knot,” the report said.

An independent investigation into the events conducted by retired chief Arthur A. Parker Jr. from Wellfleet, Mass., found that Mr. Santon’s behavior constituted multiple violations of the Tisbury police department manual.

According to the report, dated April 13, Mr. Santon improperly handcuffed the woman, left her unattended in his cruiser for more than 13 minutes, failed to report an emergency to his shift commander and lied to the investigator. The report repeatedly described his conduct as “unbecoming of an officer.”

The investigation concluded that the woman was able to remove one hand from her handcuffs and attempt suicide due to being improperly cuffed by Mr. Santon and then left unattended as he entered the jail that night.

“Officer Santon’s allowing his prisoner to remain unattended in his cruiser for over 13 minutes was totally in conflict with the training he has received throughout his career,” the Parker report said, noting the widely accepted knowledge among veteran police that the first three hours in custody for prisoners are considered a dangerous time for attempted suicides.

While the report found Officer Santon committed serious breaches of duty, it characterized his dishonesty during the investigation as the most egregious action. “Officer Santon has demonstrated that he was untruthful during this investigation. The communities served by police officers throughout the country understand that those officers are not perfect, that they can make mistakes but also have an absolute expectation that all officers are truthful,” the report said. Mr. Santon was untruthful when he denied that jail staff repeatedly inquired about the detainee, the report said. A jail staffer became concerned about the well-being of the detainee because she had previously been entered in a statewide database as a suicide risk, the report added. It further detailed that Mr. Santon was untruthful when he claimed the prisoner was left unattended for four to five minutes, instead of over 13 minutes, according to the findings of the investigation. Lastly, it said he claimed to have called the Tisbury police station to alert his shift commander, but cell phone records show he did not call the station until after the prisoner had arrived at the hospital, according to the report.

A copy of the report released to the Gazette was heavily redacted and did not include a specific recommendation for action.

While the report painted an unflattering picture of Mr. Santon, selectman Melinda Loberg said the board was presented with conflicting information during a nearly three-hour executive session on May 26, called to consider disciplinary action against Mr. Santon. Mrs. Loberg would not comment on what the contradictory evidence was. She confirmed that the selectmen took a vote at the end of the hearing, and that the vote was unanimous. But said the vote could not be disclosed because it involves a personnel matter.

Tisbury police chief Daniel Hanavan confirmed Mr. Santon returned to work on Thursday for the evening shift. He would not comment on the action taken by the selectmen or the investigation report released by the town. A phone message left for Mr. Santon was not returned by press time.

The chief confirmed a policy change for transferring detainees to the jail came out of the January incident.

“For 30 years there was not an event like this one,” he said. The new policy, endorsed by the selectmen at their Tuesday meeting, dictates that officers will secure their weapons in the trunk of the cruiser instead of inside the jail, which was past practice.

“We started a new procedure when we take someone down to the jail when they are under arrest,” Mr. Hanavan told the selectmen. “We don’t leave them by themselves at any time, they’re always going to be in our custody.”

Speaking on the phone on Thursday, the chief declined further comment other than to say: “I think overall we do a good job in the community, we have some good officers.”

Police union president and Tisbury Det. Max Sherman, who was present at Mr. Santon’s hearing, said the matter has been resolved but would not comment on the specific action taken.

“It’s over, we’d like to move on,” Mr. Sherman said.

In addition to endorsing the policy change, Tisbury selectmen requested on Tuesday that the department seek additional training, specifically in handling cases with women and immigrants. A community group, We Stand Together, had requested the town look into creating policies specifically for handling cases that involve women, immigrants and people suffering with mental health issues.

“I want to be proactive and look at what training is out there, what can our department do,” said selectman Tristan Israel.