A judge’s occupational background provides relative expertise in an issue area certain to come before them during their tenure on the bench. This is especially salient for judges who have worked as prosecutors or defense attorneys, as criminal cases make up a significant plurality of federal caseloads, even at the level of appellate courts. No scholar to date has considered how relative expertise impacts judicial diligence for cases involving relevant issue areas. Using a dataset of nearly 4,000 criminal cases over the past 25 years, I test the impact of a judge’s occupational background on two key outcomes. First, I assess whether judges with previous experience as either a prosecutor or defense attorney exert more effort when authoring majority opinions in criminal cases, counting the number of words and density of citations in the opinions as a proxy for judicial effort. Second, I consider whether, using their experiential knowledge, judges who formerly worked in criminal law are more able to convince their peers to vote with them on a criminal case, heightening levels of unanimity when tasked with authoring the majority opinion for the case. My findings shed light on the overall impact of personal characteristics on judicial decision making.