A Salvadoran man who was acquitted of criminal charges last year after claiming police brutality filed a federal lawsuit Thursday alleging Nassau County and members of its police force and sheriff's department violated his civil rights.

The suit says Willian Guillen, 34, a cook who crossed illegally into the country in 2002, was beaten and falsely arrested and imprisoned. It also says he was maliciously prosecuted and not given medical attention in jail after four days in the hospital.

Filed in Central Islip, the suit also alleges police -- particularly Criminal Intelligence Rapid Response Team members -- target minorities. Guillen's attorney, Amy Marion of Garden City, said Nassau officials encourage "aggressive police tactics," which "allows a culture of false and unjustified arrests."

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County officials quickly fired back Thursday.

"The county will not comment on this pending litigation other than to say the allegations are frivolous," County Attorney Carnell Foskey said.

The suit says Guillen suffered injuries, including broken ribs and damage to a thigh and a pelvic bone, during the March 2014 encounter. It claims police beat him at the scene of his Westbury arrest and again after ordering him to undress at a police substation -- where they allegedly hurled racial slurs and said he'd spend years in jail before deportation.

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In December, a judge found Guillen not guilty of a harassment violation and misdemeanor assault and resisting arrest -- reduced charges after what began as a felony case.

A Nassau prosecutor had said at trial that undercover cops investigating drug and prostitution complaints near a Hispanic restaurant approached Guillen after he made an apparent drug deal with another man -- before the two men ran from plainclothes officers wearing badges.

Police had said in a complaint that Guillen fled into traffic, dropping keys and a bag with a white substance believed to be cocaine. Police said they wrestled Guillen to the ground as he flailed and kicked, and found his keys but not the bag because of traffic.

The prosecutor said officers had to hit Guillen to force him to unclamp his teeth from a sergeant's thigh as he resisted being handcuffed.

Marion said at the trial that Guillen never bit the sergeant, and while he might have had bodily contact with officers, he did nothing wrong that night.

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The lawsuit says Guillen and a co-worker had ordered food at a nearby restaurant and went outside to wait before men he thought were robbers jumped out at him in the dark and he ran.

It claims two police officials who are named as defendants admitted under oath they made false statements in criminal complaints.

Internal affairs investigators completed their probe of the case, according to police spokesman Insp. Kenneth Lack, who said he couldn't comment further due to the litigation.

Guillen's attorney wrote in the lawsuit that authorities granted him a visa reserved for crime victims after his acquittal, and he got out of jail after being held months on an immigration detainer.