A literature review revealed that lying is as common or more common than honesty in modern life. The courts, police agencies, and society have acknowledged, justified, and approved the use of lying and deception by police. The present research used interviews with more than 100 police officers and a subsequent focus group of 6 police officers to specify 9 dimensions and 50 levels as categories for the factorial survey. The participants received questionnaires containing 24 unique vignettes. Each vignette depicted a typical arrest situation. The participants made judgments on each vignette. The research also included a neutralization scale and a short form of the Crowne-Marlowe Social Desirability (Lie) Scale in anticipation that some police officers would not have variability in their responses. Results of ordinary least-squares regression analysis revealed that 77 percent of the officers indicated that perjury would be probable in some of the vignettes. Police perjury varied with the job assignment and the type of crime. Female police appeared less likely to commit perjury than male officers; seniority had no significant influence. Results also revealed the common motivations and rationales for committing perjury and the factors that deterred perjury. Findings suggested that police agencies must make the elimination of police perjury and continuous education in ethics among their priorities. Further research is also recommended. Tables, appended background information and instruments, and 177 references (Author abstract modified)