Secret Signals: How Some Men Cruise for Sex

Because much of the signaling is itself benign behavior, some gay rights activists and lawyers have admonished police departments for arresting men who have done little more than tap their feet.

"Citizens have a right not to confront lewd activity in public places," said Steve Sanders, a lawyer and gay rights activist. "But if there is evidence that a sting is motivated by anti-gay animus, that may represent a more troubling issue."

At trial, Sanders said, police would have to prove that actions such as foot tapping were known signals for soliciting sex.

"What constitutes probable cause to arrest someone? If a case like this went to trial, police officers would have to produce evidence to say here is how we can say with certainty this is was really a lewd act," he said.

Craig pleaded guilty to the charges and therefore opted against a trial.

Today, Craig denied being gay and said he made a mistake by pleading guilty.

Police officers, for the most part, only investigate an area after members of the public have complained about it being used for sex, said Rich Gregson, executive director of the California Peace Officers Association.

"Police officers will investigate areas that have known histories of this sort of activity. They rely on their own knowledge and experience to tell what is happening. Most officers know the difference between an intentional signal and a stray motion," he said.

The public has a right to enter public areas without worrying about inadvertently seeing lewd acts, Gregson said. The 35-year veteran police chief said he believed this sort of activity took place "in every jurisdiction" and heard stories of "off-duty officers and even judges being caught and arrested."

With many other options available for gay men to meet each other, Gershen Kaufman, a professor emeritus of psychology at Michigan State University and author of the book "Coming Out of Shame," said public cruising is practiced mainly by deeply closeted men.

"Cruisers are not sex offenders. They are deeply, deeply closeted. There is a lot of self-hatred and shame and they can't allow themselves to come to terms with their sexuality. There is also the added element of danger and being discovered," he said.