Was encounter with Cheney a touch, a slap or a shove?

Steve Howards, 55, says he walked up to Cheney and delivered his message -- "Your policies in Iraq are disgusting" -- then lightly touched the vice president's shoulder.

The White House photographer says he saw Howards slap Cheney on the back.

Cheney's personal aide remembers Howards placing his hand on Cheney's arm and shaking his hand.

As for the Secret Service agents who arrested Howards on suspicion of assault: two say he lightly clapped Cheney on the shoulder; one demonstrated it as a shove; a fourth said Howards reached over several small children and struck Cheney.

Since the agents -- now accusing one another of changing their stories and lying about what happened -- can't agree, Cheney should give his own version, Howards said.

He has filed a federal lawsuit against the agents, claiming they violated his right to free speech and protection from unreasonable search and seizure.

"He's the so-called victim of the assault. Clearly the vice president should have very relevant testimony to give," said Howards' attorney, David Lane, who this month asked a federal judge to order U.S. marshals to serve a subpoena to the White House.

Getting the vice president in a witness box would be a historic achievement.

It's exceedingly rare for high-level officials to testify or give depositions, said Tom Fitton, president of Judicial Watch, a Washington group that advocates for transparency in government.

Fitton said he could not recall any instance in which Cheney had given a deposition while in office.

He said that to compel such a high-ranking executive branch official to testify, one must show that that official has information that couldn't be obtained in another way -- the same argument Cheney's attorney made in U.S. District Court last week.

Biz Van Gelder, a Washington lawyer who specializes in white-collar criminal defense, disagrees.

"I know of no law that says the vice president of the United States is immune from service process because he's the vice president," she said.

One question the courts will consider is how much of an intrusion it is on the schedule of the vice president to be called to testify, said Joel Goldstein, a law professor at St. Louis University and an expert on the vice presidency.