Objectives <p>Research has established that offenders are often generalists who commit a wide range of criminal offense types. Theoretical approaches to offending variety generally take a longitudinal perspective that tracks the variety of crimes committed over the life-course. Less theoretical work has been done at the microscopic scale of daily routines, though this is the scale at which individuals ultimately encounter and exploit criminal opportunities.</p> Methods <p>This paper develops a neutral model that links fine-grained offender mobility patterns in heterogeneous crime environments to offending variety. Offender mobility is modeled as Brownian motion originating from central anchor point. Crime opportunities are exploited upon encounter in a simple random fashion.</p> Results <p>The model shows mechanistically how offenders with higher mobility and/or environments with greater spatial overlap in distinct crime opportunities can display greater offending variety.</p> Conclusions <p>The model provides a neutral baseline for evaluating the relationship between day-to-day mobility, crime environments, and offending variety. The relationship displays distinctive mathematical regularities that can serve as a foundation for further theoretical development.</p>