Kevin Spacey had insisted on his innocence of the charges (File Photo)

Prosecutors dropped sexual assault proceedings against Kevin Spacey on Wednesday after the case against the Hollywood star collapsed over his alleged victim's refusal to testify.

William Little had accused the 59-year-old Oscar winner of groping him in a bar on the upscale resort island of Nantucket in July 2016.

But Massachusetts prosecutors filed a formal notice of abandonment of an indecent assault and battery indictment due to "the unavailability of the complaining witness."

Little chose to plead the Fifth Amendment, which allows witnesses not to testify so as not to incriminate themselves, after it was revealed that his cell phone -- a key piece of evidence -- may have been compromised.

Little has said he took a smartphone video of the incident, which he says took place when he was an 18-year-old busboy in the bar and restaurant.

But the phone -- which the defense wanted to examine -- has disappeared, as confirmed by Little and his parents, who were also called on to testify.

A police officer said he returned the phone after extracting all the information but admitted he neglected to ask for a receipt upon its return. The family said they never received it.

Little's mother Heather Unruh, a television news anchor in the Boston area, admitted she had deleted some potentially embarrassing photos before handing the phone over, but said she had not erased anything related to the alleged assault.

Hollywood's Reckoning

It is the latest chapter in Hollywood's reckoning over sexual assault and harassment, which has already seen television icon Bill Cosby jailed, with movie mogul Harvey Weinstein's trial set to begin in September.

Spacey had insisted on his innocence of the charges, which would have carried a penalty of up to five years in prison.

The two-time Oscar-winner -- recognized for his supporting role in "The Usual Suspects" in 1996 and his lead role in "American Beauty" in 2000 -- was considered one of the finest actors of his generation.

The case marked the first time Spacey had faced sexual misconduct charges, although it was one of more than a dozen alleged incidents to emerge since 2017 in the wake of the #MeToo movement, with devastating effect on his acting career.

He was dropped from the cast of Netflix's "House of Cards" and from a leading role in director Ridley Scott's "All the Money in the World," with Christopher Plummer brought in as a last-second replacement.

Forced out of public life, Spacey posted a video online in December in which he discussed allegations of sexual abuse in character as Frank Underwood, the scheming politician he played in "House of Cards" before the show dropped him.

"You wouldn't believe the worst without evidence, would you? You wouldn't rush to judgments without facts, would you? Did you? No, not you. You're smarter than that," Spacey said in the video.

'Free To Touch Us'

Little was working in Nantucket for the summer and had remained in the bar after his shift finished to see his hero.

After meeting the actor and telling him he was 23 years old -- the legal drinking age is 21 in Massachusetts -- he said he started drinking first beer and then whiskey at Spacey's urging.

The actor then allegedly invited him back to his place, along with some other friends. The young man declined, suspecting the actor was trying to seduce him.

But he stayed at the bar in the hopes of getting a picture with Spacey. It was then that the actor began sexually molesting the young man, according to court filings.

In addition to the Nantucket case, two other investigations are underway in Los Angeles and London, where Spacey served as artistic director of the prestigious Old Vic theater from 2004 to 2015.

Mexican actor Roberto Cavazos, who performed in several Old Vic productions, said it seemed that "it only took a male under 30 to make Mr Spacey feel free to touch us."

The first public allegation of abuse came from actor Anthony Rapp, who claimed that Spacey sexually assaulted him when Rapp was 14, in 1986.