(Reuters) - Dallas Cowboys defensive end Greg Hardy has been suspended without pay for 10 games for conduct detrimental to the National Football League, the league said on Wednesday.
The decision to ban Hardy, who last played for the Carolina Panthers, followed a two-month NFL investigation that started after the dismissal of his domestic violence case in February.
Hardy was informed in a letter by NFL Commissioner Roger Goodell that the probe determined there was "sufficient credible evidence that Hardy engaged in conduct that violated NFL policies in multiple respects."
Domestic violence charges against Hardy, who signed with Dallas last month, were abruptly dropped in February after his accuser could not be found to testify.
The jury trial for Hardy had been set to begin in Charlotte after he was accused of assaulting his former girlfriend, Nicole Holder, and threatening to kill her.
The league's probe, which involved numerous interviews with witnesses and experts, concluded that Hardy violated the NFL's personal conduct policy by using physical force against Holder in at least four instances.
"The net effect of these acts was that Ms. Holder was severely traumatized and sustained a range of injuries, including bruises and scratches on her neck, shoulders, upper chest, back, arms and feet," Goodell wrote.
"The use of physical force under the circumstances present here, against a woman substantially smaller than you and in the presence of powerful, military-style assault weapons, constitutes a significant act of violence in violation of the Personal Conduct Policy."
Several of the NFL's top players, including Adrian Peterson and Ray Rice, were charged with domestic violence in 2014, prompting the league to overhaul its personal conduct policy.
Sharply criticized for being too lenient on domestic violence and sexual assault, Goodell made the penalties for such crimes much harsher than in the past.
Hardy, a 2013 Pro Bowler who played only one game for Carolina before being suspended last season, was accused of assaulting Holder last May, sending her to the hospital emergency room.
The five-year NFL veteran was found guilty by a district court judge in July but appealed the verdict and was allowed to have a jury trial.
Prosecutors said when Holder last spoke with them in November, she told them that she "did not want to participate in another trial." Holder had already reached a civil settlement with Hardy, prosecutors said.
Hardy may appeal the NFL's decision within three days.
"You must have no further adverse involvement with law enforcement and must not commit any additional violations of league policies," Goodell wrote.
"In that respect, you should understand that another violation of this nature may result in your banishment from the NFL."
Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue