Fixing defects is an essential software development activity. For commercial software vendors, the time to repair defects in deployed business-critical software products or applications is a key quality metric for sustained customer satisfaction. In this paper, we report on the analysis of about 1,500 defect records from an IBM middle-ware product collected over a five-year period. The analysis includes a characterization of each repaired defect by topic and a ranking of developers by inferred expertise on each topic. We find clear evidence that defect resolution time is strongly influenced by a specific developer and his/her expertise in the defect's topic. To validate our approach, we conducted interviews with the product's manager who provided us with his own ranking of developer expertise for comparison. We argue that our automated developer expertise ranking can be beneficial in the planning of a software project and is applicable beyond software support in the other phases of the software lifecycle. © 2012 IEEE.