Recently, the National Police Agency of Taiwan has begun to measure performance levels for police forces across the entire island. The performance benchmarks resulting from this strategy have become the basis for allocation of government funding and other scarce resources. In this work, data envelopment analysis (DEA) was used to construct a scalar measure of efficiency for all police precincts. Further analyses on the effect of degree of urbanization and possible weight restrictions on the outputs upon the efficiency scores of each decision making unit (DMU) were conducted. In addition, a three-stage DEA model was applied to explicitly incorporate environmental factors into the DEA model. The results show that the external environmental factors specified in this study may have some effects on the efficiency scores of each district, albeit not statistically significant. Most decision making units are technically efficient; the average technical efficiency of all DMUs was as high as 98.46% when external environmental factors were accounted for.