AN ARREST IS LAWFUL IF PROBABLE OR REASONABLE CAUSE FOR THE ACTION EXISTS. PROBABLE CAUSE IS A CONCLUSION THAT A CRIME HAS PROBABLY TAKEN PLACE AND A PARTICULAR SUSPECT IS THE LIKELY PERPETRATOR; THIS PROOF IS LESS THAN THAT NECESSARY TO OBTAIN A CONVICTION, BUT ENOUGH TO JUSTIFY THE APPREHENSION, INCARCERATION, AND PROSECUTION OF THE ACCUSED. VIGNETTES SHOW THE TEMPORARY DETENTION OF AN INNOCENT CUSTOMER BY OFFICERS WHO WENT TO THE WRONG ADDRESS WHEN INVESTIGATING A REPORT OF A STOLEN CREDIT CARD, THE APPREHENSION OF AN INNOCENT BYSTANDER OBSERVING A STREET GANG FIGHT, AND THE COERCED ACQUISITION OF INFORMATION THROUGH OVERLY AGGRESSIVE POLICE WORK. THESE VIGNETTES ILLUSTRATE THE FIVE LEVELS OF PROOF IN THE PROSECUTION PROCESS. A TEMPORARY DETENTION REQUIRES A REASONABLE SUSPICION OF CRIMINAL INTENT. AN ARREST REQUIRES THAT EXISTENCE OF PROBABLE CAUSE. THE BOOKING AND INCARCERATION OF A PERSON REQUIRES A PERPETUATION OF PROBABLE CAUSE, AS DO THE SIGNING OF A CRIMINAL COMPLAINT AND THE COURTROOM PROSECUTION OF THE ACCUSED. A CONVICTION ALSO REQUIRES PROOF BEYOND A REASONABLE DOUBT. THE REASONABLE GOOD FAITH OF AN OFFICER WILL EXCUSE LIABILITY IN A FEDERAL CIVIL RIGHTS SUIT AND IN ACTIONS BROUGHT IN THE COURTS OF MANY STATES, WILL USUALLY PREVENT THE IMPOSITION OF PUNITIVE DAMAGES, AND WILL OFTEN RESULT IN A LOWER AWARD FOR COMPENSATORY DAMAGES. OFFICERS SHOULD METHODICALLY RECORD ALL FACTS AND CIRCUMSTANCES UPON WHICH THEY COULD REASONABLY BELIEVE IN THE SUSPECT'S GUILT. THE STATUTE OF LIMITATIONS FOR A CIVIL RIGHTS ACTION IS OFTEN 3 TO 5 YEARS AFTER THE ARREST--TOO LONG FOR AN OFFICER TO RELY ON HIS MEMORY ALONE. A DISCUSSION GUIDE IS PROVIDED. (MHP)