Mr Leo Caseria > Sheppard, Mullin, Richter & Hampton LLP > San Francisco, United States > Lawyer Profile

Sheppard, Mullin, Richter & Hampton LLP is proficient in acting for domestic and multinational clients in antitrust investigations, prosecutions, and enforcement actions. The team’s strong expertise with matters related to the technology sector is noteworthy, as is its focus on the intersection of antitrust and intellectual property law, which extends to topics such as patent pooling, product distribution and licensing restraints. The group is based in Washington DC and headed by Leo Caseria, whose multifaceted workload includes federal and state cartel investigations, and former DOJ official Ann O’Brien, who is recommended for the whole range of domestic, international, and multi-agency cartel matters, including federal jury trials.

Attracting client praise for its ‘tenacious litigation prowess,‘ Sheppard, Mullin, Richter & Hampton LLP’s antitrust litigation team handles international monopoly cases for large tech sector clients, as well as defending clients in antitrust merger matters and handling competitor-on-competitor disputes. Practice co-heads Leo Caseria and Ann O’Brien, praised by clients for their ‘unparalleled‘ subject matter expertise, oversee the team from the Washington DC office. Caseria has a strong record defending clients in cases involving claims of monopolization, price gouging, and conspiracy, with particular success at the early stages of litigation. O’Brien, who also leads the firm’s criminal antitrust and cartels sub-group, takes point on agency-facing litigation, leveraging her experience from working at the Antitrust Division. Michael Cohen left the firm in 2023.

Sheppard, Mullin, Richter & Hampton LLP is reputable among a wide range of businesses and private equity investors for its capacity to handle large and prolific flow of HSR filings and domestic and cross-border merger proceedings. The firm combines its active merger work with contentious and litigation expertise, representing clients in fields such as healthcare, energy, tech and manufacturing sectors. Antitrust co-chair Leo Caseria represents clients in complex merger-related litigation, while fellow co-chair Ann O’Brien, who joined the team from BakerHostetler, specializes in criminal and civil government antitrust investigations and litigation. John Carroll advises clients on US and international merger control processes, as well as government investigations. Attorneys mentioned are based in Washington DC.