THE SENSATIONAL TRIAL of San Francisco City Supervisor Dan White for the 1979 murders of Mayor George Moscone and gay activist Harvey Milk was a stranger-than-fiction scenario that any playwright would be hard pressed to devise. In "Execution of Justice" at Arena Stage, playwright Emily Mann deftly handles the sprawling, well-publicized subject matter, bringing fascinating angles of the trial and aftermath to light.

Mann allots equal time to both prosecution and defense, drawing on painstaking research, court testimony and interviews with witness. But there is no question where her feelings lie. "Execution of Justice" is a very angry play -- Mann has given it a deeply ironic title, for starters.

With this production, the age of video penetrates the sanctum of live theater. In the dazzling direction by Douglas C. Wager, the technology becomes an organic part of the drama, reflecting the media-fueled controversies and emotions surrounding the case. Wager has stationed two video cameras at corners of the stage to provide closeups of characters on a cubed screen that makes the Arena resemble a miniature Capital Centre. It's a credit to Arena's strong cast that the projected images enhance, and don't distract from, their "live" presence.

Wager also makes shrewd use of existing film footage (much of it borrowed from the Academy Award-winning documentary "The Times of Harvey Milk"). Perhaps the evening's most stirring moment is the sight of thousands of candlebearing marchers in a silent vigil, a scene Wager movingly underlines with his actors.

The drama is played out on Ming Cho Lee's set, a bare blue carpet with a flame-red square at center, riveting attention on witnesses there. In one striking image, lighting designer Allen Lee Hughes sets up a diagonal bar of light -- at one end is a cop wearing a "Free Dan White" T-shirt, at the other is Sister Boom Boom, San Francisco's notorious transvestite "nun," preaching peace but subtly threatening violence.

The cast of 19, playing 42 roles, is uniformly excellent, but several performances are noteworthy. Casey Biggs has absorbed Dan White's Irish Everyman inflections, and has a shattering breakdown during White's confession to his superiors. Stanley Anderson is powerful as defense attorney Douglas Schmidt, though his part as written seems unjustly smug and evil. Tana Hicken is taut and vivid in her three roles, in particular as high- strung City Supervisor Carol Ruth Silver. Among the witnesses, John Leonard and Kim Staunton embody impotent rage and confusion.

There are flaws. But once it gets past several dry patches and redundancies in the first act, the drama picks up the speed and force of an avalanche.

Even given the disquieting foreknowledge of the outcome, Mann endows the inevitable delivery of the verdict -- two counts of voluntary manslaughter -- with a gut-twisting power by juxtaposing it with scenes of the "White Night" riots and a barrage of shocked and enraged reactions.

Mann's play exhibits considerable intelligence and skill. But the most eloquent words come from Milk himself. Milk tape-recorded a will, to be played only in the event of his assassination, which he thought likely. In it, Milk described his murderer -- and expressed the hope that the bullet that entered his brain would "destroy every closet door."

EXECUTION OF JUSTICE -- At Arena Stage through June.