Investigations by Detectives


What are Investigations by Detectives?

What is the Evidence on Investigations by Detectives?



Seattle Police image courtesy of Flickr user jseattle and used under a Creative Commons license.

What are Investigations by Detectives?

Criminal investigations by detectives have been a hallmark of American police agencies since at least the 1950s. As Braga and colleagues note, while the technology used by detectives has improved dramatically since that time (e.g. the introduction of DNA evidence), the role and basic work of investigators has not changed dramatically. Detectives tend to be reactive and are typically assigned to make an arrest to close serious crimes after they occur.

What is the Evidence on Investigations by Detectives?

Investigations by detectives is listed under “What do we need to know more about?” on our Review of the Research Evidence. 

We have too little evidence on the work of detectives to provide a full assessment of their effectiveness. Much of what we know about detectives comes from research from the 1970s (e.g. Greenwood et al., 1977), which suggested detectives were not clearing most cases, especially property crimes. This suggests a lack of effectiveness for general follow-up investigations, a conclusion reached by the National Research Council. Indeed, based on that research, if a suspect is not caught or identified at the scene (which in many instances does not occur because it takes so long for the police to be called), it is unlikely a suspect will be identified. Current data continue to suggest that the vast majority of property crimes and a significant proportion of violent crimes go unsolved (see 2014 clearance rate data from the FBI).

Only limited recent research has examined factors that contribute to detective effectiveness.  Carter and Carter (2016), for example, examined the characteristics of homicide detectives in agencies with higher homicide clearance rates. They found these agencies tended to have certain characteristics, although these findings should be viewed as preliminary:

  • Adequate staffing- squads of approximately one supervisor and four investigators and enough squads so each investigator is the lead for about three homicides per year
  • Sufficient training and preparation- ideally at least three years in patrol and two years as a general detective
  • Gathering as much information at the scene as possible, which is easier when witnesses/the community trust the police
  • Use of crime and intelligence analysis
  • Access to adequate technology/equipment
  • Strong relationships with patrol, other units, other law enforcement agencies, community partners

Braga and colleagues (2011) have recently called for a greater focus on the potential crime control benefits of detectives. Although the evidence they cite to support this call is largely anecdotal, the initial results are promising. As they conclude “investigators can generate tremendous value when involved in strategic crime-control efforts. Many investigators have rich insights on recurring crime problems and can be used much more creatively in dealing with the underlying conditions, situations and dynamics that cause crime problems to persist” (Braga et al., 2011: 19).

Telep (2011) echoes these conclusions in his proposal for more rigorous research on police investigators and police informants, arguing that the work of detectives can be better integrated into patrol work. For example, police could combine hot spots enforcement with efforts to recruit and maintain informants in drug crime hot spots as a way to better incorporate patrol officers into investigatory work and detectives into hot spots policing.

Recent work as part of the Matrix Demonstration Project has focused on trying to increase the effectiveness and efficiency of investigators by making detectives more oriented towards high-crime places (and not just individual suspects).  Examples of the approach from Richmond and (Tate et al., 2013) Minneapolis (Koper et al., 2015) suggest in-depth problem analysis in high crime locations may be a useful approach to involve detectives in crime reduction efforts.


Evidence-Based Policing Matrix


Investigation by Detectives Studies in the Evidence-Based Policing Matrix

Fox & Farrington (2015) The burglary arrest rate for the treatment department increased from 11.3% pretest to 30.1% posttest, whereas in the control agencies, it declined from 15.9% to 10.9%.

Resultfull-circle = successful intervention; grey-circle = mixed results; empty = nonsignificant finding; backfire = harmful intervention

Rigor: M = moderately rigorous; R = rigorous; VR = very rigorous

X-axis: I = individual; G = group; MP = micro place; N = neighborhood/community; J = jurisdiction

Y-axis: F = focused; G= general

Z-axis: R = reactive, P = proactive, HP = highly proactive