LOS ANGELES — Sheppard, Mullin, Richter & Hampton announced on Tuesday that by the end of this week, the firm will have laid off 25 attorneys since the beginning of the year.

According to an e-mailed statement, some terminations were performance-related while others were “true ‘lay-offs,’ done in order to adjust professional staff levels in practice groups whose level of business has been adversely affected by the economic downturn. The terminations have been carried out incrementally over the last two months, because firm management has very carefully assessed each associate’s performance in the context of the level of work projected for the associate’s practice group.”

The layoffs were first reported on the blog Above the Law.

The Los Angeles-based firm grossed $352 million in revenues in 2008, up by 6%, but revenue per lawyer fell by 4% to $765,000. Last month, three partners specializing in white-collar criminal defense and one partner specializing in intellectual property, all from Mayer Brown, joined Sheppard Mullin. The firm has more than 500 lawyers in 11 offices.