Spectators in the Arlington County courtroom stared at the color television monitor. On the screen, Daniel R. Kfoury, charged with first-degree murder in the death of his housemate, Robert C. Bloom, dropped to his knees to show detectives how he crouched for nearly seven hours, Bloom's head wedged between his legs, as he tried to exorcise demonic spirits.

"I made him do this by the authority of the word of God," Kfoury explained in a calm, conversational tone. "Sometimes I had to strike him harder than a tap . . . sometimes you had to give him a good healthy blow . . . I wanted to get this animal, this beast out of him."

The two-hour videotape, made by Arlington detectives when they interviewed Kfoury after Bloom's death last October, was played at a pretrial hearing last week. Arlington Circuit Judge Paul F. Sheridan ruled Friday that prosecutors can show it to the jury when Kfoury goes on trial later this year.

As in Arlington, courts across the country have entered the video age.

Although videotapes have been used in court for more than a decade, their popularity has increased greatly in recent years as the technology has become less expensive and more familiar.

"Virtually every lawyer now has a video deck at home and many have cameras," said David Balabanian, a San Francisco lawyer writing a book about the use of videotapes in civil lawsuits. "It's a pretty natural step now for lawyers to start experimenting with the equipment."

In criminal cases, police departments and prosecutors are increasingly turning to videotapes as a valuable weapon in their arsenal of trial techniques. Instead of simply taking down defendants' statements and testifying to them in court, police videotape suspects in major cases to let jurors watch and listen for themselves.

They turn video cameras on those stopped for drunk driving to demonstrate the drivers' degree of intoxication, and bring the cameras to crime locations to record the scene, sometimes complete with bodies. In more than half the states, children in sexual abuse cases may have their testimony videotaped to spare them the added trauma of testifying in court.

In civil cases, personal injury lawyers prepare "day in the life" videos to show jurors the pain and hardship suffered by their injured clients. And, in increasing numbers, they tape "settlement brochures" -- sometimes with melodramatic musical soundtracks -- to convince defendants to settle before the case can get to the jury.

Witnesses who might have to testify about the same facts at a number of trials, such as expert witnesses in asbestos cases, are videotaped and replayed at each trial. The latest legal video craze is computer-generated re-creation of accidents; for example, a videotape of an airplane crash that depicts the plane's path along with a soundtrack of the cockpit conversation and subtitles so jurors can read along.

"Videotape makes a more dramatic impact," said Georgetown Law Center professor Paul F. Rothstein, an evidence expert who has studied the use of videotapes in court. With a videotaped confession, he said, instead of having jurors read a defendant's statement or listen to a police officer's account, "It's the defendant himself sitting there saying, 'I did it. I plunged the knife in,' " he said.

Lawyers attribute the power of videotape to the fact that they are trying cases in the age of television. "It has strengths that are far beyond any substance," said Mark Dombroff, a lawyer at Hughes, Hubbard & Reed's Washington office who is an expert on the use of "demonstrative" evidence. "The likelihood is that when the case is over that day they're going to go home and watch the news on television. They're accustomed to receiving information from television, a large part of which they believe."

Not surprisingly, most criminal defense lawyers hate doing battle against videotapes.

"It's straight from the horse's mouth," said J. Andrew Chopivsky, who represented Calvin L. Alston, one of several defendants in the murder of D.C. resident Catherine L. Fuller who gave police a videotaped statement. "They are seeing this defendant, who may choose not to testify at the trial actually testifying before them in response to police interrogation."

Chiefly because of the videotape, Alston pleaded guilty to second-degree murder rather than face trial, Chopivsky said. "It was because of the way Calvin appeared on that screen," he said. "He appeared to be comfortable, didn't appear nervous, appeared very straightforward. He would have been the best witness against himself."

In pretrial motions to suppress the use of the videotapes and trying to discredit them at trial, videotapes can remove much of defense lawyers' room to argue that their clients were coerced into confessing.

"If the videotape is played, it's catastrophic for your case. You can literally lose your case" because of a videotape, said Wendell Robinson, who represented another of the videotaped Fuller defendants. Trying to defend a client who has given a videotaped statement, he said, "is sort of like saying, 'I want you to represent me on the sale of my house,' and they've already signed a contract."

"Of course they hate it," said a D.C. law enforcement official. "A trial is a search for the truth and there isn't much better proof of what happened in a situation than a videotape of it.

"All defense attorneys think anything that proves to a jury their client is guilty is prejudicial, and the answer to that is, 'You bet,' " the official added. "It takes away from them the . . . threads they can use to conjur up reasonable doubt. It totally destroys that avenue of obfuscation which is so much a part of the defense function."

Despite that, the official said, police and prosecutors are divided over video's value as a law enforcement tool. "There are innumerable evidentiary questions that come to rise," the official said. "If tapes are lost, then there's the whole question of what was on the tape; if there are gaps on the tape, there are questions about what it said."

A one-hour videotaped statement became the centerpiece of the monthlong murder trial of Paul Leon Jordan last year and pointed up some of the benefits and risks of videotapes. On the tape, Jordan told police how he "started cutting on" Cora Barnes, a 56-year-old baby sitter, and then stabbed a 3-year-old child, Crystin Fletcher, because "she saw what was what so I had to take care of it, too."

"On that videotape, in clear, coherent, intelligible English, Mr. Jordan says he's the one who did it," prosecutor Amy S. Berman told jurors in closing arguments, when she replayed parts of the videotape.

But defense lawyer James H. McComas used the videotape -- which showed Jordan at points shaking so violently he could hardly grasp the cup of water he was trying to drink from -- to argue that at the time he gave the confession, Jordan was so debilitated by alcohol withdrawal he confessed to a crime he did not commit.

"What you're seeing is what police got out of him after seven, eight hours of interrogation, lies, false promises, tricks and psychological coercion," McComas said in his closing argument.

Jordan was convicted and sentenced to 40 years to life in prison, and the videotape is now the focus of his appeal, in which he claims the trial judge erred in letting jurors see the tape.

Even video proponents agree the tapes can be misused, either by manipulating what is shown on the tape or simply because the medium itself is so powerful it can overwhelm the other evidence in a case.

In videotaping a deposition or another statement, "Who do you point the camera at?" Balabanian asked. "Can you zoom in on the witness to show his or her beetling brows and fidgeting fingers? . . . . Camera angles, lighting, can be manipulated -- intentionally or unintentionally -- to make the witness look good or bad."

In August, the 9th Circuit U.S. Court of Appeals overturned the conviction of a man found guilty of child molestation because the jury was permitted to replay the videotaped testimony of the 5- and 7-year-old children involved in the case during its deliberations. "Videotaped testimony is unique," the court said, terming the replay of the videotapes "equivalent to allowing a live witness to testify a second time in the jury room."

Still, courts routinely accept videotaped evidence, and evidence experts said they expected the use of videotapes to grow.

"Television and videotape is a very compelling medium. Advertisers wouldn't pay the kind of rates they pay it if weren't," Dombroff said. Lawyers, he said, "are finally waking up to the fact that they are selling the position and point of view of their client over someone else's point of view, and television is a very persuasive means for packaging a point of view."