A surveillance camera captured the shocking moment inside a sterile hospital room: A veteran Chicago police officer appeared to push a patient with his hands cuffed behind his back violently into a wall.

As Rayshon Gartley bounced off the wall, Officer Clauzell Gause, with the department nearly 10 years at the time, allegedly punched him flush on the face with a sweeping right hand.

Gartley, involuntarily admitted to Jackson Park Hospital for a mental health evaluation, collapsed onto a bed on his right side. The 6-foot-6, 235-pound Gause held Gartley down with his right hand while striking him with two swipes with his left hand, Cook County prosecutors said in charging the officer with official misconduct.

It was over in less than 10 seconds. The surveillance video appeared to show that another officer witnessed the attack. Five hospital personnel entered the room just seconds later to find Gartley lying prone on the bed.

In spite of the video’s clarity, Cook County State’s Attorney Kim Foxx’s office quietly dropped the felony charges that Gause had been facing for more than three years, saying it couldn’t go to trial that day because the victim had repeatedly refused to cooperate and show up in court.

“We cannot proceed and meet our burden without the testimony of Mr. Gartley,” Assistant State’s Attorney Kenneth Goff said moments before Judge James Obbish granted a prosecution motion to “nolle pros” the case — drop the charge, according to a transcript of the brief June 20 hearing.

Then-State’s Attorney Anita Alvarez’s office had charged Gause in May 2016, two months after the two-term officeholder lost the Democratic primary to Foxx, a reform candidate whose campaign centered on criticism of Alvarez for not aggressively prosecuting police misconduct.

The video of Gartley’s beating, made public shortly after Gause’s first court appearance, made headlines in a city still raw from the fallout over the fatal police shooting of 17-year-old Laquan McDonald that sparked protests and a push for police reform.

Andrew Stroth, an attorney who represented Gartley in a lawsuit that the city settled for $175,000 last year, was surprised to learn from a Tribune reporter that prosecutors had dropped the two criminal counts against Gause, saying the officer “unjustifiably” beat Gartley and should be “held criminally responsible for his actions.”

Gause’s attorney did not return calls seeking comment.

At the court hearing June 20, Goff said prosecutors had made “numerous attempts” to speak to attorneys who represented Gartley in the lawsuit in an effort to contact Gartley, but the lawyers never returned their calls, according to the transcript.

Stroth, however, denied that claim, saying he didn’t recall anyone from the state’s attorney’s office trying to contact him or his partner in the case.

He also disputed prosecutors’ characterization that Gartley was uncooperative, saying he was simply hesitant to relive “one of the most traumatic events that’s ever happened to him.”

Stroth also questioned the decision to drop the charges, given the strength of the video and the existence of additional evidence.

Officer Leshawn Hawkins, who witnessed the attack, was available in court to testify, Goff noted at the hearing last month.

If Hawkins defended Gause’s actions, the prosecution could have used the video to undercut his testimony.

“I think anyone could look at that video and make a determination that it’s excessive force. I understand where they’re coming from,” Stroth said of the prosecutors. “I just think there’s other evidence that supports prosecution. … To just drop the charges? That’s not appropriate given the situation.”

Gause, who has been on paid desk duty since shortly after the beating five years ago, now faces the possibility of disciplinary action for the beating.

The Civilian Office of Police Accountability, which investigates allegations of police misconduct, is continuing its probe into the incident, according to a spokeswoman.

The incident took place in June 2014 after one of Gartley’s family members called police to a house on the Far South Side asking for help because Gartley was off his medication, according to court records.

After Gartley was involuntarily admitted to Jackson Park Hospital for a mental health evaluation, prosecutors said, he suddenly stood and punched Gause in the face as medical personnel took his blood pressure.

Another officer quickly restrained Gartley and handcuffed him.

But that alleged assault was not captured on surveillance cameras, and Gartley’s lawsuit claimed it never happened. Instead, the suit alleged, Gause had taunted Gartley, slammed him to the floor without warning and beat him — all before entering the empty observation room, where the attack caught on camera took place minutes later.

“Rayshon suffered great pain and physical injury and trauma to his head, face, wrists, arms, shoulders, legs and torso,” the suit said of Gartley, described as more than a foot shorter and 75 pounds lighter than Gause. “He suffered great emotional distress, which exacerbated the condition that brought Rayshon to Jackson Park Hospital in the first place.”

There were early hints that Gartley might not be a reliable witness even beyond why he ended up at the hospital. Prosecutors did not approve charges against Gause until two years after the attack — in part because Gartley could not be located, authorities said at the time.

At last month’s hearing, Judge Obbish noted that Gartley had never once been in court since the case was charged.

Even if Gartley had taken the stand, Gause’s attorney appeared to have plenty with which to attack his credibility, including convictions for aggravated battery and robbery, court records show.

The attorney also coult have tried to undermine his reliability by pointing out any inconsistencies in his testimony compared with what he said in his deposition from his lawsuit.

Richard Kling, a longtime defense attorney and professor at Chicago-Kent College of Law at Illinois Institute of Technology, said a clever prosecutor can find a way to work without putting a recalcitrant or less than ideal witness on the stand — especially with the existence of a video.

“If it’s a creative prosecutor ... you’ve got it on videotape, and you’ve got another officer willing to testify,” Kling said. “I don’t know what the problem would be.”

But other lawyers told the Tribune that a damning video alone won’t always be enough for a conviction.

Longtime criminal defense attorney Jennifer Blagg said Gartley’s participation at trial might have been especially important if the defense made claims that could not be refuted by the video itself.

“A video really just shows a tiny flash of the entire context,” she said. “It’s like the flash of a camera. You have the flash of that moment, but there’s moments before it and there’s moments after.”

David Gaeger, also a criminal defense attorney, found the video a bit choppy, enough to make it hard to determine if Gause’s fist hit Gartley’s face, he said.

“While it is clear as day to the average citizen who’s watching it, in terms of proof beyond a reasonable doubt in court you’d need a victim to corroborate, say, ‘Yeah, that hand made contact with my face,’” Gaeger said. “Videos seem to tell tales, but with a high burden (of proof), they don’t always. ... You would just hope that (prosecutors) evaluate every case, not just cases against police officers, in the same method.”

Gartley’s testimony could also have been vital since the video contains no audio.

In court last month, prosecutors said they had been trying to contact Gartley for months but had only been able to reach his mother — who said she didn’t know his whereabouts.

In March, prosecutors finally located Gartley in Cook County Jail, where he was being held on a probation violation, records show.

Goff, the prosecutor, said Gartley told prosecutors during an interview at the jail that he did not want to come to court on Gause’s indictment. After his release from custody, prosecutors subpoenaed Gartley twice to appear in court, but he never showed up.

“He was aware that if he did not show, the state would have no choice but to dismiss this action,” Goff told the judge last month.

Gause would have faced probation or two to five years in prison if he had been convicted of official misconduct.

With the charges dropped, Judge Obbish advised Gause to “look upon this as a new start.”

“Yes, sir,” Gause replied, according to a transcript.

“Not as anything other than that,” the judge said.