Physical Evidence, Forensic Evidence and the Prosecution of Sexual Assault

The University of Illinois Children and Family Research Center will undertake a study that builds on ongoing NIJ-funded research in Massachusetts that examines the relationship of physical and forensic evidence in sexual assault cases to arrests and criminal charges. This study will collect the same type of crime laboratory and medical examination data as in the prior study, but will add to that data from prosecutor files on the use of physical and forensic evidence in prosecution criminal justice outcomes like case dismissals, guilty pleas, convictions, and sentence length.
The proposed project will consist of a random sample of 300 sexual assault cases with adult or adolescent victims in the city of Boston, Massachusetts for which criminal charges of sexual assault were filed between 2005 and 2011 and an evidence collection kit was completed. The University of Illinois will obtain crime laboratory files, Provider Sexual Crime Reports (PSCR), police reports, and prosecutor cases files for each of the 300 cases in the sample.
The University of Illinois will use descriptive statistics to examine how frequently both specific physical and forensic variables and the total array of such evidence are probative or exculpatory. Logistic regression analysis will examine the relative contribution of specific types of biological evidence (sperm, amylase, blood) and DNA evidence to probative value. Analysis will also examine the probative value of other evidence such as toxicology results and non-medical physical evidence. This analysis will be augmented with interviews of Assistant District Attorneys regarding the probative value of particular forensic and physical evidence.
The research team will also examine whether Sexual Assault Nurse Examiners (SANEs) are more likely to produce physical and forensic evidence and whether evidence in their cases is more probative. To the extent that SANEs and other medical providers see different cases, logistic regression analysis will examine the impact of SANE on evidence and probative value controlling for case differences.
The final set of analyses will examine the relationship between physical and forensic evidence collected during forensic medical examinations and criminal justice outcomes. Crosstabs will examine how a) physical and forensic evidence in general and b) probative physical and forensic evidence are associated with dismissals, guilty please, convictions, and sentences. Additional regression analyses will examine what factors are associated with sentence length. ca/ncf