After watching "America's Most Wanted," Maxwell's coworkers decided that he looked like a fugitive California schoolteacher who had molested his fifth-graders, and they tipped the local police. Officers arrived, cuffed Maxwell, and took him to the station. They rolled his prints, which conclusively established that Maxwell was not the guy.
Maxwell sued for unlawful arrest. The officers argued that they had only temporarily detained Maxwell for printing, and that he had never technically been arrested. But the court simply invoked the de facto arrest rule: "The officers themselves acknowledge that they handcuffed Maxwell and took him to police headquarters for fingerprinting. This is the 'functional equivalent' of an arrest." Finding that the coworkers' tips did not amount to probable cause, the court denied immunity to the officers and sent them to trial.
Alternatives
So what exactly should you do? In many cases like Davis, Dunaway, Hayes, and Kaupp, you may have the right guy in your sights and need only a fingerprint exemplar, a photograph, or a statement in order to develop the probable cause to make a formal arrest. But the last thing you want to do is have your case turn out like these cases did, with a conviction reversed, or a lawsuit filed, or both.
In addition to the obvious steps (running for warrants, checking DMV or DPS records, invoking parole/probation terms), you may have to consider simply asking the suspect to come to the station voluntarily, in his own transportation. (If you think he's a flight risk, be sure to have surveillance in place when you call him-if he runs, his flight may justify detention. (See Illinois v. Wardlow.)