The right to a trial by jury is at the center of our justice system. Jury trials also are central to television drama. From the days of “Perry Mason” to the new series “The Jury,” viewers have come to expect courtroom tension arising out of the spirited prosecution and defense of the accused. But according to the hourlong documentary “The Plea” on “Frontline” (8 p.m., PBS), our conception of jury trials is about as realistic as the dancing baby on “Ally McBeal.”

According to figures cited on “The Plea,” only a tiny fraction of all criminal cases result in a jury trial. An astounding 95 percent of cases result in plea-bargaining. And, according to the judges, lawyers and prosecutors interviewed here, it’s the only way the courts can work. If a higher number of defendants demanded a jury trial, the system would collapse.

But while plea-bargaining keeps the system going, it may not result in justice. In several of the cases presented here, defendants who professed innocence felt they were coerced into pleas by lawyers too busy to examine their cases, or judges who told them point-blank that they would receive the maximum sentence if they were convicted after a jury trial.

• “Introducing Graham Norton” (8 p.m., Comedy Central) offers viewers a half-hour glimpse at the Irish-born talk-show host whose series “The Graham Norton Effect” debuts Thursday. It will be the first hourlong show in the network’s history.

Norton’s British talk show “So Graham Norton” has been a hit on BBC America. Norton manages to combine a quick wit and a decidedly off-color sensibility with genuine warmth.

Norton also has a way of cajoling the most embarrassing stories out of members of his studio audience. But despite his penchant for the bawdy, he rarely ventures into pure raunch. It should be amusing to see how he fares with an American audience.

Tonight’s other highlights

• A man who abused refugees from Cuba is found slain on “CSI: Miami” (7 p.m., CBS).
• A spoilt rich girl throws herself at the lifeguard on “North Shore” (7 p.m., Fox).
• Sugarcult and Kanye West perform on “Pepsi Smash” (7 p.m., WB).
• Tru’s meddling causes the death of an innocent bystander on “Tru Calling” (8 p.m., Fox).

Late night

Vince Vaughn, Britton Keeshan and Los Lobos on “Late Show with David Letterman” (10:35 p.m., CBS).