The police need probable cause to make an arrest in Colorado. If the circumstances, evidence, and observations would give a prudent person the belief that a suspect has committed a felony or misdemeanor, then the police can make an arrest. However, if the police do not witness the criminal activity, they may have to go to a judge to get a warrant to make an arrest. The police and prosecutors may submit evidence and affidavits to support their case and if the judge finds probable cause, they may issue a warrant to arrest the suspect. In some cases, a traffic stop can lead to an arrest.