For two years, state Trooper Nicholas J. Holden of the Brookfield barracks did something many social justice activists and police watchdogs have fought for: video and audio recorded his encounters with people he stopped.

However, he made the recordings without official state police approval, failed to turn most of them over to prosecutors during court proceedings, and is now facing serious discipline, according to interviews and documents obtained by the Telegram & Gazette.

“I thought it would be helpful,” the then 13-year-trooper told a Worcester Central District Court judge Sept. 8, 2014, of his decision that morning to turn over video of a field sobriety test before a hearing.

Under questioning by the defendant’s lawyer, Trooper Holden admitted he did not routinely turn over his tapes to prosecutors, a withholding of evidence a Massachusetts Bar Association expert said might constitute obstruction of justice.

By November 2014, the district attorney had sent out letters to more than 100 defendants notifying them of potential evidence issues, and a long-running investigation into the trooper was launched.

“State Police Internal Affairs investigators have sustained several charges against Trooper Nicholas Holden related to his unauthorized audiotaping and videotaping interactions with members of the public,” David Procopio, director of media relations for state police, wrote in a statement Friday. “The charges sustained by the department are in stark contrast to the values and standards of conduct demanded by the Massachusetts State Police.”

State police - who do not customarily record cruiser stops - declined to release internal affairs records from the probe, saying they are not yet public records because the case is in the disciplinary stage.

In a statement Friday, the office of District Attorney Joseph D. Early Jr. said after it learned of the issue, it ordered the trooper to preserve all of his recordings and turn them over to the State Police Crime Lab as evidence.

“We are not aware of any case where Trooper Holden failed to disclose to the people stopped that they were being recorded,” Mr. Early's office wrote. “This matter has been referred to the state police.”

In an interview last week, Timothy J. Connolly, Mr. Early’s communications director, said there was no evidence Trooper Holden broke the law.

Trooper Holden declined comment for this story.

Mr. Connolly said he was not aware of any of the 104 cases affected by the taping – most of which occurred between 2011 and 2014 – being reopened as a result. He said it was not immediately possible to say whether any cases were negatively affected but that that the office didn't receive much blowback from defense attorneys after mailing the notices.

The defendants whose cases spawned the September 2014 disclosure by Trooper Holden were brothers arrested following an encounter in Worcester with Trooper Holden, who stopped one of them for a bad headlight on March 29, 2014. The stop turned into a drunken driving probe.

One brother, Aladdin Connolly, of Shrewsbury, was charged with drunken driving, while the other brother, Eric Connolly of Atlanta, Georgia, who was following in a car behind, was arrested after police alleged he disrupted their investigation.

At a joint hearing seeking dismissal of charges, and later at Eric Connolly's trial, Trooper Holden and others gave testimony that raises questions about who in the state police, and who in the district attorney's office, knew about his taping and when.

On Sept. 8, 2014, attorneys for the brothers were set to argue that their cases should be dismissed after alleging that troopers confiscated and illegally deleted a cellphone video that Eric Connolly had taken of Aladdin Connolly during field sobriety tests.

Trooper Holden - who had a dash cam recording video and a microphone attached to his person recording audio - turned over his material to a prosecutor the morning of the hearing. Assistant District Attorney Shayna L. Woodard then used it to argue the allegation of destruction of evidence was moot because a tape of the stop had been produced.

Under cross-examination by the brothers’ attorneys, Trooper Holden said he had been taping for about two years with his own equipment donated to him by the West Brookfield Police Department.

“For my safety and for court-related purposes,” the trooper responded when asked why he taped. He added he had turned over tapes to the DA before, but was prevented from elaborating after Ms. Woodard objected to the question.

During a trial months later, Trooper Holden testified he had only turned over a tape to the DA once before; he was not asked when that happened.

Records on file in Central District Court show Trooper Holden disclosed the existence of a cruiser video following a separate impaired driving arrest from January 2014 - 10 months before the DA's notices to affected defendants went out. In a statement of facts filed in court, Trooper Holden noted he activated his cruiser dash camera "to record the event." Court paperwork shows the man's defense requested the cruiser DVD in a pre-trial conference on Feb. 24, 2014.

Mr. Connolly, of the DA's office, said in his interview with the Telegram & Gazette that it was his understanding the office acted swiftly after it was made aware of Trooper Holden’s taping, but would check into the matter further this week.

Testimony at the Sept. 8, 2014, Connolly brothers' hearing make it clear at least one superior state police officer knew of Trooper Holden’s taping.

“I told him I didn’t see it as a problem,” Sgt. Alvin D. Toney Sr. testified. Sgt. Toney, now retired, testified he had known about the taping for about two years but did not authorize it.

Trooper Holden testified that he asked someone in the state police for permission to record; but when he was asked who he asked, he replied, “I don’t know the person’s name.”

During trial months later, Trooper Holden, when asked which superior officer had authorized the camera installation, replied, “none.” The trooper further testified he told a lieutenant at the scene of the brothers’ March 29, 2014, arrest that he was recording them.

State police declined to comment on superior officers’ knowledge of the taping or when state police headquarters was made aware, citing the ongoing nature of its disciplinary actions against Trooper Holden. Asked Friday whether the state police learned of any other state troopers recording encounters with the public, Mr. Procopio said he was not aware of any such cases but could probe the matter further this week.

State police said recording of traffic stops is not expressly prohibited in state police regulations, but neither is it allowed.

“Installation of audio and video equipment that was not issued by the department would be prohibited without authorization,” Mr. Procopio said.

Stephen J. Weymouth, a Boston criminal defense attorney and expert with the Massachusetts Bar Association, said Trooper Holden’s failure to disclose recordings was an improper withholding of evidence that could have hurt a defendant’s case should a recording have included evidence beneficial to that person.

“It could conceivably rise to the level of obstruction of justice,” Mr. Weymouth said, although police officers or prosecutors are rarely charged with such a crime.

Mr. Weymouth said in his opinion, it’s likely that if the recordings had a large impact on a case or cases, it would have bubbled up publicly before now.

Contacted Friday, Michael S. Hussey, who runs the state’s public defender office in Worcester, said he could not think of any such cases offhand. He said he remembered one case in which Trooper Holden turned over a video to a client, but could not recall the name of the case or whether it had an impact.

“It was a dumb thing of him to do on his own without approval of his supervisors,” Mr. Hussey said of the recordings. “It would certainly have been improper to not have turned it over in every case.”

In the case of Aladdin Connolly, Trooper Holden admitted on the stand to several discrepancies between the field sobriety test depicted on the video and what he wrote in his official report. He attributed the discrepancies to being in a rush on a busy Friday night and not having time to review the tape prior to writing his report, as was his custom. Mr. Connolly’s case was dismissed after Trooper Holden failed to appear at a court hearing in December 2014.

“The court does not condone Trooper Holden’s failure to advise the Commonwealth of the existence of his cruiser video equipment or the belated production of the video in this case,” Judge Janet J. McGuiggan wrote in one ruling on the case.

Mr. Connolly’s brother, Eric Connolly, was arrested for allegedly disturbing the peace and then struggling with officers following his brother's arrest. His lawyer alleged that prior to his arrest, Eric Connolly was taking video on his smartphone, an act that irked a trooper who subsequently confiscated his phone prior to the scuffle.

Sgt. Toney testified that Eric Connolly was holding a cellphone in his hand, while Judge McGuiggan ruled that Trooper Holden’s recording included statements from Eric Connolly complaining about his cellphone being taken.

Additionally, two relatives of the Connollys testified they saw a trooper scrolling through the phone without a warrant at the Holden barracks - where the brothers were booked - before pulling down a privacy shade. However, Judge McGuiggan denied a motion the brothers had filed seeking to dismiss their cases based on destruction of evidence.

“There is no evidence that a video was ever successfully recorded,” she opined, noting while witnesses attested to seeing Mr. Connolly recording, no witness testified as to ever seeing the actual video.

Eric Connolly's first trial ended in a mistrial after a witness, under the state's questioning, referenced the internal affairs probe into Trooper Holden, a subject the judge had barred from the case. After a second trial, he was convicted of several charges, including disturbing the peace and disorderly conduct. He filed a notice of appeal but never formally appealed.

In a document admitted to the court record, a juror from the first trial made his thoughts on the case clear in messages he wrote to the Connollys’ sister.

“FYI, the entire jury spoke today and we were gonna find (him) not guilty unanimously,” the juror wrote. “I wish you all well going forward as I genuinely believe both your brothers were screwed over by the police.”

Trooper Holden is currently on desk duty while the video probe and a second, unrelated probe into a different complaint against him is adjudicated, state police said.

Richard J. Rafferty, Trooper Holden’s attorney, did not return a phone message left Friday. West Brookfield Police Chief C. Thomas O’Donnell confirmed selectmen voted to donate the equipment to Trooper Holden around 2010.

“He’s always worked well with our people,” Mr. O’Donnell said of the trooper, who was honored with the State Police Medal of Lifesaving in 2007.

According to a news release from that event, Trooper Holden was credited with saving two victims of a car accident in Westfield in October 2006 after climbing into a wrecked vehicle to administer first aid.

A summary of Trooper Holden’s disciplinary record provided by state police to the Telegram & Gazette in a public records request shows he has been the subject of 11 internal affairs investigations since he was hired in 2002. The record includes more exonerations than sustained allegations.

State police only listed "action" as being taken following one of the probes, a case from 2003. It is not possible to determine what, if any, discipline was ordered in that case, because police, citing personnel privacy laws, redacted that section of the record.

Contact Brad Petrishen at brad.petrishen@telegram.com. Follow him on Twitter @BPetrishenTG.