Many states allow individuals to be civilly committed as “sexually violent predators” if a judge or jury determines they are likely to engage in a sexual offense once released due to a mental abnormality or personality disorder. To be committed, the evidence must demonstrate that the person in question has serious difficulty controlling his behavior, and evidence of psychopathy is frequently introduced in these cases. However, some have voiced concern that there is no guidance regarding how to define or assess volitional control, that experts often reach different conclusions in these cases, that predicting future behavior is difficult to assess, and that evidence of psychopathy might bias the factfinder. The current study examined whether a psychopathy diagnosis or the presence and content of expert testimony regarding these concerns would influence participants’ sentencing decisions and attitudes about the person on trial. A 2 (diagnosis) x 3 (defense expert testimony) design was employed and mock trial testimony from an SVP trial was presented to 184 undergraduate students. Although psychopathy diagnosis and defense expert testimony did not significantly impact the primary dependent variables of interest, exploratory analyses yielded significant findings regarding gender differences, perceptions of volitional control, and factors that influenced participants’ decisions. Implications and avenues for further research are discussed.