Another Patent Trial and Appeal Board specialist has left Knobbe Martens.

Bridget Smith, a former co-chairwoman of the PTAB group at Knobbe, is joining Lowenstein & Weatherwax, an 11-lawyer boutique in Los Angeles specializing in administrative challenges to patent validity.

Lowenstein & Weatherwax has defended patents held by owners such as Rockstar Consortium US LP, Maxim Integrated Products Inc., Seven Networks LLC, and IXI IP LLC against attacks from companies such as Apple, Google, Samsung and JPMorgan Chase & Co. Despite its size, the firm ranks No. 20 on Unified Patents' list of patent owner counsel at the PTAB, which is part of the U.S. Patent and Trademark Office. Knobbe ranks No. 8.

"We're thrilled to have Bridget join our team," partner Nathan Lowenstein said in a statement. "She's an exceptional and experienced PTAB litigator and a well-known expert in the field."

Smith is a trained chemical engineer who began work as a software engineer at Motorola Semiconductor Products and then as a data scientist consultant at Khimetrics Inc. before getting her law degree at Arizona State.

She said the Lowenstein firm has "garnered a tremendous reputation and record before the PTAB against top-notch competition, an incredible achievement for a firm with just 10 lawyers. This is a great opportunity for me to grow the PTAB practice with Nate & Ken."

Smith is at least the third Knobbe partner who's held a leadership role in its Patent Office Litigation Group to leave the 275-lawyer firm in the last year. Brenton Babcock joined Womble Bond Dickinson last fall, and Michelle Armond left in May to start Armond Wilson.

Smith had been with Knobbe for 12 years. "I leave behind many friends and colleagues at Knobbe Martens, an extraordinary firm, where I began my career," she said. "I'm excited to be working with Ken, Nate and the other attorneys at Lowenstein & Weatherwax LLP."