He has a long-standing interest in the relationships between aging, mutagenesis, and cancer. His past work includes discoveries that proliferation or transcription is required for nuclear DNA repair and mutation; he provided the most conclusive evidence for existence of the mutator phenotype in human cancers; he determined that polymerase-induced mitochondrial DNA point mutations do not drive aging; and he revealed that human cancers exhibit decreased mitochondrial DNA mutagenesis relative to normal tissues. For this work he has developed novel technologies, including adapting transgenic technologies to measure DNA adducts and mutation in mice; inventing the Random Mutation Capture (RMC) assay to quantify mutations in any DNA-based organism, including mtDNA point mutations and deletions; and development of a novel qPCR-based DNA damage detection assay. Moreover, his lab recently established an exceptionally sensitive next generation sequencing (NSG)-based mutational assay.