Sean O'Brien Law
12_Sean O'Brien_web.jpg


Criminal Defense Trial Attorney


Nothing is more important than loyalty to the client.

At Sean O'Brien Law, that loyalty is evident through relentless preparation, client communication, and an aggressive approach to litigation. A former prosecutor with extensive litigation and trial experience, he understands what it takes to win.

Mr. O'Brien has extensive experience trying cases in courtrooms throughout Chicago and Illinois in both state and federal courts. Prior to forming O'Brien & Murphy-Aguilú, Mr. O'Brien defended criminal matters ranging from traffic cases to murder charges as an Associate Attorney for one of the largest criminal defense firms in Chicago. There, Mr. O'Brien concentrated his practice on large narcotics cases.

For the first portion of his career, Mr. O'Brien served as a prosecutor in the Cook County State's Attorney's Office where he gained significant experience trying motions and trials for complex narcotics cases as a Special Prosecutor in the Narcotics Bureau.

Mr. O'Brien has tried hundreds of bench trials, jury trials, and motions.  He is an expert in narcotics, search and seizure law, traffic, appeals, forfeiture cases, and expungements.




1739 S Halsted St. 1F
Chicago, IL 60608

(312) 600-5875
(312) 626-2461 (fax)


Specialized Areas of Practice

Felonies and misdemeanors

posession of drugs


involuntary manslaughter

fleeing and evading police

dRIVING uNDER the influence

driving with suspended/ revoked license



Results, communication, value. That is how Sean beat my case and I couldn’t be happier with my choice in attorney.
— Chris, former client


Let's Talk.

Use the form below to contact Mr. O'Brien regarding your legal enquiry. To help best service your enquiry, please be as detailed as possible. You may also email or call us to make an appointment.

Your information will not be shared with any third-party for any reason.

Name *