WASHINGTON — If jurors at the perjury and obstruction-of-justice trial of I. Lewis Libby Jr. are looking for reasons to acquit the former chief of staff to Vice President Cheney, they have a lot to choose from.

Mr. Libby ‘s defense, led by Theodore Wells Jr. and William Jeffress Jr., has offered a hodgepodge of arguments, including innocent failures of memory on the part of the defendant and similar shortcomings in the recollections of prosecution witnesses. The defense also has advanced at least three seemingly separate conspiracies involving NBC News journalists, CIA and State Department officials, and White House aides protecting President Bush’s top political adviser, Karl Rove.

The prosecution case, by contrast, was fairly linear and straightforward. The special prosecutor, Patrick Fitzgerald, presented a series of witnesses whose stories or notes seem to contradict Mr. Libby’s claims about how he acquired and dispensed information about the identity of a CIA officer, Valerie Plame.

Lawyers not involved in the case said it is common for the defense to offer a myriad of arguments, while the prosecution is more focused.

“You throw out as much as you can, hoping to get one juror,” a top criminal defense lawyer in Manhattan, Edward Hayes, said. “People like conspiracy theories.”

“It’s not inconceivable you could get a couple of jurors to say, ‘I don’t think he’s guilty because of memory. We all forget some things,'” another prominent defense lawyer, Benjamin Brafman, said. “A couple of jurors might not like that argument but might be persuaded by the suggestion he’s a sacrificial lamb and the administration is protecting Rove.”

However, the scattershot approach sometimes makes juries lose trust in a defense lawyer and view him or her as someone wildly making excuses for a client who must be guilty.

“I think you have to be very careful throwing defenses into a case,” Mr. Brafman said. “Fitzgerald is going to look at the number of defenses and comment on that. If something was made in their opening statement and they didn’t deliver, he has the right to comment on that.”

Mr. Hayes said the defense has to be cautious about suggesting that all the prosecution witnesses are out to get Mr. Libby. “What you can’t do is argue that every single witness is a bad person, lying, and out to hurt somebody. That’s just too much,” the defense attorney said.

Most defense lawyers interviewed by The New York Sun said they agreed with the defense’s decision not to put Mr. Libby or Mr. Cheney on the stand.

Mr. Brafman noted that Mr. Libby’s eight hours of grand jury testimony were played to the jury, so calling him would have been superfluous and perhaps reckless. “They’ve heard his explanation. To repeat the explanation and subject him to cross-examination is pointless. Either they believe his explanation or they don’t,” Mr. Brafman said.

Mr. Hayes said some jurors of modest means might look askance at the team of high-priced legal talent surrounding Mr. Libby. At least five attorneys questioned witnesses on the defendant’s behalf. “I usually prefer having one lawyer do all that work,” he said.

Away from the jury, Judge Reggie Walton has taken a few jabs at the size of the defense’s in-court team, which amounts to about a dozen lawyers and support staff. In fairness, though, the government team appears to be roughly the same size. Closing arguments in the month-long trial are set for Tuesday.

As the lawyers argued yesterday over proposed jury instructions, the defense team added some emphasis to its memory argument, asking Judge Walton to instruct the jurors that the defense asserts outright that Mr. Libby’s memory failed him, not just that it “may have” done so. The move seemed to concede that at least one of Mr. Fitzgerald’s witnesses is telling the truth about discussing Ms. Plame with Mr. Libby.

Mr. Libby’s decision not to testify at trial led the judge to rule that the defense may not argue that specific terrorist threats or international crises so distracted Mr. Libby that he forgot discussions about Ms. Plame. However, the defense will be permitted to tell jurors that Mr. Libby’s weighty and important workload hampered his memory. Mr. Fitzgerald dismissed the judge’s restriction as “semantics” and expressed confidence that Mr. Wells will find a way to suggest to the jury that the issue of the CIA officer paled in comparison to the crises Mr. Libby was juggling.

One of the factors most favorable for the defense is that the prosecution must prove beyond a reasonable doubt that any false statements Mr. Libby made to the FBI or the grand jury were intentional and not the product of mistake or memory failure. This requires not just guessing what was in Mr. Libby’s head, but being all but certain about it.

“Perjury is a very difficult crime to prove without some form of corroboration,” such as documents or recordings where the defendant boasts of lying or discusses a plan to deceive, Mr. Brafman said.

Legal observers said one of the biggest strengths of Mr. Libby’s defense is not a strategy or a tactic but simply the presence of Mr. Wells at the helm. “Ted Wells is probably one of the most eloquent criminal defense lawyers in the United States. He’s a very charming man,” Mr. Brafman said. “He’ll probably deliver one of the best summations anyone has ever seen in any case.”