[5] As a young man Hallinan developed, in the words of California Supreme Court Justice Raymond E. Peters, a "habitual and continuing resort to fisticuffs to settle personal differences.

While attending the London School of Economics, he was arrested with Lord Bertrand Russell during a Campaign for Nuclear Disarmament sit-down demonstration in front of the U.S.

[10] In the fall of 1963, he joined the Ad Hoc Committee to End Discrimination and participated in sit-ins at the Sheraton Palace Hotel, Mel's Drive-In, and the Van Ness Avenue Cadillac showroom.

[6] After graduating from UC Hastings, Hallinan's criminal history proved an obstacle to his admission to the California State Bar.

[6] His mother, however, testified that Hallinan became violent in response to the bullying caused by his father's vocal support of labor leaders during the Red Scare.

[7] California State Assemblymen Willie Brown and John L. Burton both testified that Hallinan possessed good moral character.

Justice Peters found that if the court denied professional licenses to everyone who engaged in a sit-in "we would deprive the community of the services of many highly qualified persons of the highest moral courage."

[12] Hallinan successfully defended the Diggers after they were arrested for giving away free food on the steps of San Francisco City Hall.

[17] In 1988, Hallinan left private practice for a political career, first serving for seven years on the San Francisco Board of Supervisors and then as district attorney.

[19][20] On July 16, 2018, when he was 81 years old, Hallinan was suspended for failing to pass a professional responsibility exam and was henceforth not eligible to practice law.

[8] In the 1995 elections the police union and both the city's daily newspapers endorsed recently fired senior prosecutor Bill Fazio against incumbent district attorney (DA) Arlo Smith.

Hallinan successfully forced and won a runoff election for DA through a campaign run by his longtime aide Ross Mirkarimi.

[22] The former defense attorney promptly fired 14 senior prosecutors, leaving pink slips on their chairs during lunch, then posted an armed guard outside his new office in the Hall of Justice.

[8] Prominent Irish real estate developer Joe O'Donoghue confronted Hallinan about the firings while attending a birthday party at Izzy's Steaks and Chops.

After a nationally publicized trial that had to be moved to Los Angeles, Hallinan's prosecutors, former Jesuit priest Jim Hammer and Kimberly Guilfoyle Newsom, won the conviction.

[29] The SFPD leadership was indicted by Hallinan after a bar fight involving assistant police chief Alex Fagan's son.