Rob Nigh, the former Tulsa County chief public defender, died on Sunday.
Nigh who was 57, died months after stepping down for serious health issues.
He served as chief public defender for two years before resigning.
Rob Nigh represented Oklahoma City bomber Timothy McVeigh and witnessed his 2001 execution. And defended Michael Bever, charged with killing five members of his Broken Arrow family with his brother Robert.
He was known for his encyclopedic legal knowledge, work ethic and intense preparation on every case he handled.
In a statement, Tulsa County District Attorney Steve Kunzweiler said:
"Rob Nigh stood for something beyond himself. He was a fierce advocate of the rule of law on both sides of the courtroom. He led by example in everything he did."
The Associated Press contributed to this report.