COMPAS is a fourth-generation risk and needs instrument combining static criminal history data with dynamic criminogenic factors such as social environment and employment, producing general recidivism, violent recidivism and pretrial misconduct scores. Designed for correctional case management and rehabilitation planning, its use expanded into judicial sentencing.

Its legal position is defined by State v Loomis, in which the Wisconsin Supreme Court held that a sentencing court may use a COMPAS risk assessment as a relevant factor but that it cannot be determinative, and required cautionary warnings about the instrument's limitations to accompany its use. That ruling remains the leading US authority on algorithmic risk evidence in sentencing.

The Public Safety Assessment, developed with support from Arnold Ventures and available without a commercial vendor, takes a deliberately narrower approach. It uses nine factors drawn only from age and criminal history, explicitly excluding any interview, community ties, neighbourhood or marital status, and produces three estimates: failure to appear, new criminal arrest, and new violent criminal arrest while on pretrial release. Scores are provided to the accused, the judicial officer, defence and prosecution. It was piloted from 2013, released publicly in 2018 after five years of testing, built on around 750,000 cases from roughly 300 jurisdictions and validated on more than 500,000.

The contrast between the two is instructive: one is a proprietary multi-factor instrument whose inputs are not fully public, the other a deliberately minimal open instrument that excludes socio-economic factors by design. Both are used to inform decisions about individual liberty.