Application of plant DNA markers in forensic botany: genetic comparison of Quercus evidence leaves to crime scene trees using microsatellites

As highly polymorphic DNA markers become increasingly available for a wide range of plant and animal species, there will be increasing opportunities for applications to forensic investigations. To date, however, relatively few studies have reported using DNA profiles of non-human species to place suspects at or near crime scenes. Here we describe an investigation of a double homicide of a female and her near-term fetus. Leaf material taken from a suspect's vehicle was identified to be that of sand live oak, Quercus geminata, the same tree species that occurred near a shallow grave where the victims were found. Quercus-specific DNA microsatellites were used to genotype both dried and fresh material from trees located near the burial site and from the material taken from the suspect's car. Samples from the local population of Q. geminata were also collected and genotyped in order to demonstrate that genetic variation at four microsatellite loci was sufficient to assign leaves to an individual tree with high statistical certainty. The cumulative average probability of identity for these four loci was 2.06x10(-6). DNA was successfully obtained from the dried leaf material although PCR amplification was more difficult than amplification of DNA from fresh leaves. The DNA profiles of the dried leaves from the suspect's car did not match those of the trees near the crime scene. Although this investigation did not provide evidence that could be used against the suspect, it does demonstrate the potential for plant microsatellite markers providing physical evidence that links plant materials to live plants at or near crime scenes.     

Can You Build a Better Cop?

Research Summary

By drawing from psychology and economics, we present an experimental evaluation of a procedural justice training program designed to “slow down” police officers’ thought processes during citizen encounters. We find that officers who were randomly assigned to participate in training were as engaged in the community as similarly situated officers, but they were less likely to resolve incidents with an arrest or to be involved in incidents where force was used. These changes were most evident among officers who worked in areas with a modest level of risk.

Policy Implications

Police officers who are actively engaged with the public can reduce crime through general deterrence and by arresting criminals. Nevertheless, excessive discretionary arrests and the use of force by officers can reduce public trust in the police. To date, there is scant evidence as to how police departments can successfully train officers to balance enforcement and public trust in the field. Through our study, we demonstrate that a relatively minor supervisory intervention may cause substantive changes in how police and citizens interact with each other.     

Can text messages reduce incarceration in rural and vulnerable populations?

Reducing failures to appear (FTA) in court is a top priority for criminal justice practitioners and advocates. However, existing work on reducing FTAs through text message reminders focuses on large urban jurisdictions and defendants who are housed. Using a field study in Shasta County, California, we evaluate whether text message outreach can increase court appearances for housed and unhoused populations. We find housed defendants randomly assigned to the treatment group were 10% less likely to miss their next scheduled court date than defendants in the control group. We find no statistical difference in the FTA rate of unhoused individuals assigned to treatment or control groups, and cannot rule out large positive or negative effects. We find that improving the quality of contact information in court records could lead to large reductions in FTAs. Partnering with local social service providers may not, but more research is needed.