LOS ANGELES—Leave it to Steve Martin to turn jury duty into performance art. Tweeting over the last couple of days, Martin has regaled his 380,000-plus followers on Twitter with observations inspired by the legal process unfolding before him.

Using his Twitter name @SteveMartinToGo, the actor and comedian, a prospective juror, at 12:10 p.m. Monday tweeted: "REPORT FROM JURY DUTY: defendant looks like a murderer. GUILTY. Waiting for opening remarks." A follower named @luvjack713 warned: "If you're really on jury duty you could get into trouble tweeting from it AND announcing he's guilty!!! Careful Steve!"

He quickly responded: "(I'm kidding) Shhhh....." And then he kept at it: "REPORT FROM JURY DUTY: guy I thought was up for murder turns out to be defence attorney. I bet he murdered someone anyway."

While the jokes may be original, the conduct isn't. Reuters Legal last week reported that judges granted new trials or overturned verdicts in dozens of criminal and civil cases due to jurors' online diversions, and bored citizens waiting for jury selection are tweeting, blogging and otherwise venting in growing numbers.