NEW YORK -- The NFL is immediately implementing a sweeping domestic violence initiative under its personal conduct policy that calls for a six-game suspension for a first offense and a lifetime ban from the league for a second offense.

The measures, announced in a letter from NFL commissioner Roger Goodell to all team owners, a copy of which was obtained by ESPN, apply to all NFL personnel.

A six-game suspension would be without pay and the length of the penalty could increase in these cases: an employee was involved in a prior incident before joining the NFL; violence involving a weapon; choking, repeated striking, or when the act is committed against a pregnant woman; or in the presence of a child. A second-time offender may petition for reinstatement after one year but there is no assurance the petition would be granted, the letter said.

A league source told ESPN's Andrew Brandt that discipline would be triggered by adjudication of a player's case, such as a conviction or plea agreement. The policy is not retroactive, meaning all personnel have a clean slate, a league source told ESPN's Mark Dominik. If a player commits a crime while in college or high school and then has a first offense while in the NFL, the player could be subject to a suspension harsher than six games.

The measures come partly in response to intense criticism Goodell received for his handling of discipline for Baltimore Ravens running back Ray Rice, who received a two-game suspension in July for assaulting his then-fiancee in February. Widely viewed as a soft punishment, Goodell left many with the impression that the NFL did not understand domestic violence or take it seriously as a crime.

Goodell acknowledged as much in the letter.

"At times, however, and despite our best efforts, we fall short of our goals," Goodell wrote. "We clearly did so in response to a recent incident of domestic violence. ... My disciplinary decision led the public to question our sincerity, our commitment, and whether we understood the toll that domestic violence inflicts on so many families. I take responsibility both for the decision and for ensuring that our actions in the future properly reflect our values.