Johnston allegedly arranged a meeting with a woman at a hotel through Craigslist, and upon meeting her said that he was a cop and flashed an ID and badge.
Then he made sexual advances and comments, making the woman suspicious of his claims and credentials. After following Johnston outside to get a better description, he fled, and the victim called 911.
Johnston was also suspected in an earlier robbery and sexual assault at a hotel in Milpitas.
San Jose police tracked Johnston to Fremont, where he was arrested with the help of local police. Further investigation also turned up an ID and badge that may have been used in the crime.
Johnston is being held on bail in Santa Clara County jail.
Jackson West is willing to bet the perp was trying to prey upon sex workers whom he figured wouldn't call the proper authorities.