(WASHINGTON) -- Federal lawmakers and activists urged approval Thursday of a bill that would make it illegal to depict cruel treatment of animals for commercial purposes.

"It's beyond horror; it's evil," actress Loretta Swit, who represented Actors and Others for Animals and the Humane Society, told the House Judiciary Committee's crime panel.

The panel viewed a "crush video" - part of what witnesses called a multimillion dollar, worldwide industry - that showed a woman stomping a guinea pig to death. A half-dozen people at the hearing walked out as it played, while others covered their ears to block out the animal's squeals.

"In all my years of pushing legislation to protect animals, this is clearly one of the sickest forms of animal cruelty I have ever heard of," said Rep. Elton Gallegly, R-Calif.

Prosecution under local animal cruelty laws is rare because it's difficult to identify the people who make and appear in the videos.

Gallegly's proposed legislation would enable federal prosecutors to go after those who market the films by making it illegal to create, sell or possess any depiction of animals being treated cruelly for commercial purposes. Violators could get up to five years in prison.

More than 2,000 titles of "crush videos" are available, selling for $30 to $100 each, Gallegly said, adding: "This windfall must end."

Critics contend the bill would violate the First Amendment's guarantee of free speech. They say it is so broad it could allow prosecution of those who make legitimate animal documentaries and even distributors of news magazines that contain pictures of bullfights.

Gallegly said he would offer amendments to exempt educational or artistic works such as films of bullfights.

Rep. Robert Scott, D-Va., questioned how local authorities would know to enforce the law if the videos were shot in other states or countries.

But Tom Connors, deputy district attorney in Ventura County, Calif., said the bill would work the same as prohibitions against the possession or sale of child pornography.