Mark E. Mulligan graduated from Oak Harbor High School in 1970 and continued his education at the University of Toledo where he received a bachelor degree in Business Administration in 1974. In 1977 Prosecutor Mulligan graduated from the University of Toledo with his law degree.

Prosecutor Mulligan had a private practice from 1977 until his election as Ottawa County Prosecutor in 1997. In addition to his private practice, Mulligan worked part-time for the Prosecutor's Office from 1989 until 1997.

Among the many innovations in the prosecutor's office, those of which Prosecutor Mulligan is most proud include the creation of the Victim Advocacy program, providing support and crisis intervention for victims of crime, 24 hours a day; the implementation of a juvenile diversion for those who have committed a criminal offense, but who the prosecutor believes will not offend again, providing speedy restitution for the victims and positive rehabilitation for the offender; designing and distributing an internet safety brochure which protects innocent youth from internet predators; and sponsoring prevention programs such as metal detectors for schools, free gun locks for Ottawa County citizens, and funding for police equipment and training.