Taking the bench as an interim judge on the New York Supreme Court, O'Brien deals with the case of a seaman (Alejandro Rey) accused of murdering a co-worker with a longshoreman's hook. Gene Hackman plays the prosecutor in the case.
O'Brien's negotiations for the Viktor Emblem get more complicated when the person holding it has his life threatened.
Protesting their living conditions, the prisoners of the state prison's isolation cell block have taken 3 hostages whom they will only release if O'Brien will make a public presentation of their case.
O'Brien represents a spiritualist in the murder of a wealthy client whose death he has predicted.
Accountant Jerry Quinlan was an apparent suicide, until it is discovered that he had questions and suspicions about his company's books which he was about to report.
A foster father (John McGiver), who is content to keep collecting welfare checks, hires O'Brien to keep seven children with him after an adoption judge takes the youths away from him.
O'Brien tries to have a will declared invalid before three greedy heirs (Angela Lansbury, George Rose and Thayer David) kill each other in a house that's booby-trapped from cellar to attic.
An eccentric judge (Burgess Meredith) engages O'Brien to represent him on charges of mental disability that could remove him from the bench. Guest stars: Robert Emhardt, Barnard Hughes, and Ken Kercheval.
A burlesque comedian (Milton Berle) is involved in murder when his straight man is killed after making advances on the comedian's wife.
O'Brien represents a movie producer (Alan Alda) who was charged with resisting arrest while filming an "underground" movie. Guest stars: Claude Akins, Charles Grodin, Jessica Walter, and Joanna Pettet.
While being bugged by his ex-wife to sign the lease on her luxurious apartment, O'Brien must defend a client involved in a fatal shooting that follows a fixed horse race. Guest stars: Martin Sheen, Tony Roberts, and Philip Bosco.
A "heist artist" who is accused of fatally stabbing a dealer of rare violins is defended by O'Brien. Guest stars: Norman Fell, Dana Elcar, Kurt Kasznar, Frank Langella, and former boxer Jake LaMotta.
O'Brien investigates the death of a partner in the Seventh Avenue Dress House where his ex-wife works. Guest stars: Lou Jacobi, Theodore Bikel, Simon Oakland and Alice Ghostley.
O'Brien is retained by a Mother Superior in order to persuade the owner of an adjoining cafe to permit St. Anthony's Youth Center to use its garden.
A woman (Cloris Leachman) is accused of murdering her husband, and retains O'Brien to defend her. Guest star: Robert Loggia.
After discovering that a man is dating his ex-wife (Joanna Barnes), O'Brien delightedly sets him up as a "pigeon" in order to trap a killer. Guest stars: Roger Moore and Michael Constantine.
O'Brien's English bookie is charged in the death of an accountant, but the person who can clear him is nowhere to be found.
Eva Grimaldi (Mary Tahmin) cons the con: she borrows $2500 from her boyfriend Ollie Maxwell (Buddy Hackett) to ransom her millionaire father, who is being held prisoner in Latin America.
O'Brien represents a client who was charged with murder after being released from prison. Guest star: Vincent Gardenia
The Trials of O'Brien is a 1965 television series starring Peter Falk as a sordid Shakespeare-quoting lawyer and featuring Elaine Stritch as his secretary and Joanna Barnes as his ex-wife. The series ran for only 22 episodes. Among its guest stars: Milton Berle, Robert Blake, David Carradine, Faye Dunaway, Britt Ekland, Tammy Grimes, Buddy Hackett, Gene Hackman, Frank Langella, Angela Lansbury, Cloris Leachman, Roger Moore, Rita Moreno, Estelle Parsons, Joanna Pettet, Brock Peters, Tony Roberts and Martin Sheen. Falk often said that he actually liked this financially unsuccessful series much better than his later smash-hit Columbo.