One in an occasional series on celebrities who bring their star power to Washington on behalf of a pet causes. Monday’s visitor: Sean Penn.

Sean Penn testifies on Capitol Hill in Washington on Monday. (Susan Walsh/AP Photo)

Event: House Human Rights Subcommittee hearing (in the Rayburn Building) on Jacob Ostreicher, an American detained in Bolivia since 2011.

Setting: Mostly empty hearing room with one chair and mike at the witness table, because Penn was the only witness — essentially, a tricked-out news conference.

Bona fides: Oscar-winning actor, paparazzi pugilist, global human-rights activist.

Backup: Rep. Chris Smith, who’s made two trips to Bolivia in attempts to get Ostreicher freed; four other congressfolk; congressional staffers/fans.

U.S. actor SeanPenn pushes U.S. businessman Jacob Ostreicher in a wheelchair, wearing a flak jacket, during a recess at Ostreicher's hearing in Santa Cruz, Bolivia, Tuesday, Dec. 11, 2012. A Bolivian appeals panel has refused to immediately release Ostreicher, despite evidence he was fleeced and extorted by prosecutors who have had him jailed for 18 months without charges on suspicion of money laundering. Ostreicher has been hospitalized for more than two weeks in a private clinic after being diagnosed with Parkinson's. Ostreicher's case led to the uncovering of a shakedown ring allegedly run by the No. 1 legal advisor in the Interior Ministry, and including two prosecutors. It came after actor Sean Pean interceded with President Evo Morales. (AP Photo) Penn pushes U.S. businessman Jacob Ostreicher in a wheelchair during a recess at Ostreicher’s hearing in Santa Cruz, Bolivia last year. (AP Photo)

What Penn wants: The release of the ailing Ostreicher, a New York businessman accused of money laundering; although imprisoned, he has never been formally charged by the Bolivian government. Several high-level government officials have been arrested for allegedly extorting him, but he remains under house arrest. After investigating the case, Penn testified that he was “personally and thoroughly convinced” of Ostreicher’s innocence.

How he got involved: Actor/pal Mark Wahlberg asked him to look into the case. “It came at a point I could pay attention to it — and then I couldn’t stop paying attention to it.” He made a high-profile trip to Bolivia in December, but failed to get Ostreicher out despite a close relationship with President Evo Morales.

How he looked: Weary, like he needed a good night’s sleep. Navy suit, white shirt, tie askew, messy hair.

How he sounded: Passionate, knowledgeable, very engaged, respectful. Able to answer detailed questions on his feet.

Hail Mary pass: Penn unveiled a surprise plan to make this a global cause by pressuring international corporate sponsors of the famed Dakar Rally — scheduled to run through southern Bolivia next year — to pull the race out of the country unless Ostreicher is released.

Sound bite: “I’ve never seen a worse movie or more archvillainy on a such a caricaturish or humanly diabolical level.”

Read more about recent celebvocates and even more about celebvocates from past years.

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