 In 2013, he became Associate Head of the Department of Sociology and Criminology there, serving until 2019.Perhaps Ulmer's best known and most influential research has focused on criminal court prosecution and sentencing.In the late 1990s, Darrell J. Steffensmeier, Ulmer, and John H. Kramer developed the “focal concerns” theoretical model of sentencing and criminal justice decision making, which describes criminal punishment decisions as driven by prosecutors' and judges' interpretations of defendants' "blameworthiness," assessments of defendants' "dangerousness" to the community, and perceptions of "practical constraints" surrounding criminal cases.