Given fragmentation between mental health and criminal justice systems, we tested the feasibility of implementing a potential new form of pre-booking jail diversion. Our “linkage system” consists of three steps: (i) individuals with serious mental illnesses and an arrest history give special consent to be enrolled in a statewide database; (ii) if an officer has an encounter with an enrolled patient and runs a routine background check, he or she receives an electronic message to call; and (iii) the “linkage specialist” provides brief telephonic assistance to the officer. Of 206 eligible individuals, 199 (96.6%) opted in, the database received 679 hits, and the linkage specialist received 31 calls (and in at least three cases an arrest was probably averted). The mean number of arrests was 0.59 ± 0.92 in the year before enrollment (38.7% arrested) and 0.48 ± 0.83 during the 12-month intervention (30.7% arrested). Implementation is feasible, and a signal that the system might reduce incarceration was detected, encouraging development of a larger study.