I'm currently playing a lawyer in a PF home game, and I focused entirely on the social skills, Sense Motive, Knowledge: Local, and Profession: Lawyer (Barrister, but why quibble). The social skills are for cross-examinations and interrogations, the Sense Motive because witnesses lie, Knowledge: Local covers knowledge of humanoid culture and laws, and Profession: Lawyer because I don't work pro bono.
Really, any class with access to most of these will do, but I went specifically with a Infernal Sorceror, because of the flavor. Recently I just pumped him to uber-lawyer with two simple feats: Skill Focus (oratory) and Eldritch Heritage: Imperious. The skill bonuses from the entry-level bloodline power are almost tailor-made for a sorceror lawyer. You will be able to court expensive clients better (Cha bonus to Diplomace and KN: Nobility), outmaneuver your rivals on the other legal team (Cha bonus to KN: Local), and cite historical precedents better (Cha bonus to KN: History), so long as the cases in question are human-centric. If you're an elf, dwarf, or any other race, it's only worth a few extra class skills. Also, it doesn't help with Bluff, Intimidate, or Sense Motive, so it doesn't add much to the dramatic courtroom confrontation with the witness/victim/murderer. The bonus from SF:Perform can help sway a judge or jury, though, so that helps.