Joseph Walsh, former assistant general counsel at Exxon Mobil Corp., has joined Am Law 100 firm Duane Morris as a trial partner in Houston and New York.

Walsh, who joined the firm on Monday, said he enjoyed his time in a number of in-house roles at Exxon Mobil, which is headquartered in Spring, Texas, but looks forward to returning to private practice at a firm he knows well.

Matthew Taylor, chairman and chief executive officer at Duane Morris, wrote in a press release that the firm is pleased Walsh selected the firm for the next phase of his career after nearly two decades at Exxon Mobil.

"Joe Walsh is a nationally prominent litigator and environmental attorney and a great example of the type of marquee talent who adds significantly to our platform," Taylor wrote.

Sharon Caffrey, a co-chair of Duane Morris' trial practice group, wrote that Walsh brings "significant and broad experience" as a first-chair trial lawyer in state and federal courts, and knowledge of regulatory and policy issues.

Several factors drove his decision to join Duane Morris, Walsh said, including a strong desire to return to private practice, after cycling in and out of law firms and positions at Exxon Mobil. He said he is very familiar with Duane Morris and its lawyers, because the firm is outside counsel for Exxon Mobil.

Also, Walsh said, Taylor is a longtime friend, as they met as freshmen at Boston College more than 40 years ago.