When Claude Saunders was found stabbed to death in his bunk at the Adult Correctional Institutions here, state police pulled three of Rhode Island's most well-known criminals from their cells, ordered them to strip and sloshed a chemical onto their chests, arms and shoulders.

It "felt cold and tingled," recalled Douglas Gomes, a prisoner with a long record of assults and armed robberies. The sensations didn't stop until he was allowed to shower the chemical off, he said.

But Sydney Clark, a convicted rapist, and Tyrone Powell, a kidnapper and extortionist looked down at their chests where blue spots appeared.

The spots meant that the chemical had detected the presence of blood. Partly on the strength of the test evidence, Powell and Clark were convicted of the Nov. 2, 1979, murder of Saunders.

But now Clark, Powell and Gomes have turned the tables and have charged the state police with trying to kill them.

The chemical police used on their bodies was benzidine, widely considered one of the most dangerous cancer-causing chemicals known.

It is so carcinogenic and is absorbed so quickly through the skin into the bloodstream that even a single-exposure to a small amount can result in cancer years later, according to some experts.

Benzidine is so dangerous that the National Institute for Occupational Safety and Health will soon urge that the chemical, sometimes used as an industrial dye, be banned in the United States, according to Maurice Herbert, an agency spokesman.

Gomes, in a federal court suit that has been joined by Clark and Powell, contends that the test violated constitutional protections against cruel and unusual punishment and unreasonable search and seizure.

Gomes said his shoulders and chest broke out in a rash and sores a week after he was given the forensic test, and while those conditions have cleared up, he now lives in fear of cancer.

It is uncertain how many other suspects in violent crime cases may have been subjected to the test in Rhode Island. The state police won't say.

What is known from state police sources is that the department began administering the test in 1973, the same year the U.S. Occupational Safety and Health Administration listed the chemical as one of 14 industrially used substances dangerous enough to require special emergency restrictions. The following year, the agency issued standards requiring workers using the chemical to wear "impervious garments, including gloves and boots."

About this time, police sources said, most other police departments are believed to have stopped use of the test.

Col. Walter Stone, Rhode Island state police supertendent, said that beginning in January the department has tested suspects' skin for victims' blood by rubbing their skin with damp swabs and then dropping the swab into benzidine to watch for a color change. He would not say whether the application of benzidine was halted then or at some earlier date.

David DeFanti, director of the state crime lab at the University of Rhode Island, said in an interview that he believes brief exposure to the chemical is harmless. He said he takes no special precautions when using the substance. DeFanti, along with the state police, is a defendant in the prisoners' suits.

Experts who claim that even a single exposure can lead to cancer, particularly bladder cancer, include Walter F. Rowe, professor of forensic science at George Washington University, and Walter Trool, professor of psysiological science at the New York University graduate school.

In one study cited by Trool, 80 percent of workers involved in manufacture of the chemical were found to develop bladder cancer 20 to 30 years after exposure. Normal incidence of the disease is one case per 100,000 people.