Evaluation of the Phoenix, Arizona, Homicide Clearance Initiative, 2003-2005

The purpose of the study was to conduct a process and outcome evaluation of the Homicide Clearance Project in the Phoenix, Arizona Police Department. The primary objective of the Homicide Clearance Project was to improve homicide clearance rates by increasing investigative time through the transfer of four crime scene specialists to the homicide unit. In 2004, the Phoenix Police Department received a grant from the Bureau of Justice Assistance providing support for the assignment of four crime scene specialists directly to the department's Homicide Unit. Responsibilities of the crime scene specialists were to collect evidence at homicide scenes, prepare scene reports, develop scene diagrams, and other supportive activities. Prior to the project, homicide investigators were responsible for evidence collection, which reduced the time they could devote to investigations. The crime scene specialists were assigned to two of the four investigative squads within the homicide unit. This organizational arrangement provided for a performance evaluation of the squads with crime scene specialists (experimental squads) against the performance of the other squads (comparison squads). During the course of the evaluation, research staff coded information from all homicides that occurred during the 12-month period prior to the transfers (July 1, 2003 - June 30, 2004), referred to as the baseline period, the 2-month training period (July 1, 2004 - August 31, 2004), and a 10-month test period (September 1, 2004 - June 30, 2005). Data were collected on 404 homicide cases (Part 1), 532 homicide victims and survivors (Part 2), and 3,338 records of evidence collected at homicide scenes (Part 3). The two primary sources of information for the evaluation were investigative reports from the department's records management system, called the Police Automated Computer Entry (PACE) system, and crime laboratory reports from the crime laboratory's Laboratory Information Management System (LIMS). Part 1, Part 2, and Part 3 each contain variables that measure squad type, time period, and whether six general categories of evidence were collected. Part 1 contains a total of 18 variables including number of investigators, number of patrol officers at the scene, number of witnesses, number of crime scene specialists at the scene, number of investigators collecting evidence at the scene, total number of evidence collectors, whether the case was open or closed, type of arrest, and whether the case was open or closed by arrest. Part 2 contains a total of 37 variables including victim characteristics and motives. Other variables in Part 2 include an instrumental/expressive homicide indicator, whether the case was open or closed, type of arrest, whether the case was open or closed by arrest, number of investigators, number of patrol officers at the scene, number of witnesses, and investigative time to closure. Part 3 contains a total of 46 variables including primary/secondary scene indicator, scene type, number of pieces of evidence, total time at the scene, and number of photos taken. Part 3 also includes variables that measure whether 16 specific types of evidence were found and the number of items of evidence that were collected for 13 specific evidence types.

本研究旨在对亚利桑那州凤凰城警方凶杀案侦破项目的过程与结果进行评估。该凶杀案侦破项目的首要目标是通过对四名犯罪现场专家的调任至凶杀案组，以增加调查时间来提升凶杀案侦破率。2004年，凤凰城警方从司法援助局获得了一项资助，该资助用于直接将四名犯罪现场专家分配至警方的凶杀案组。犯罪现场专家的职责包括在凶杀案现场收集证据、编制现场报告、绘制现场图以及其他辅助工作。在项目实施之前，凶杀案调查员负责证据收集，这减少了他们可以投入调查的时间。犯罪现场专家被分配至凶杀案组内四个调查小组中的两个。这种组织安排为具有犯罪现场专家的小组（实验组）与其他小组（对照组）的绩效评估提供了可能。在评估过程中，研究人员对转移前12个月（2003年7月1日至2004年6月30日）发生的所有凶杀案的信息进行了编码，这一时期被称为基线期。此外，还包括了为期2个月的培训期（2004年7月1日至8月31日）和为期10个月的测试期（2004年9月1日至2005年6月30日）。收集了404起凶杀案（第一部分）、532名凶杀案受害者及幸存者（第二部分）以及3,338份犯罪现场收集的证据记录（第三部分）。评估的主要信息来源是警方的记录管理系统——警务自动化计算机输入系统（PACE）的调查报告和犯罪实验室的信息管理系统（LIMS）的犯罪实验室报告。第一部分、第二部分和第三部分各自包含衡量小组类型、时间周期以及是否收集了六类一般证据的变量。第一部分共包含18个变量，包括调查员数量、现场巡逻警员数量、目击者数量、现场犯罪现场专家数量、现场收集证据的调查员数量、总证据收集者数量、案件是否开放或已结案、逮捕类型以及案件是否因逮捕而开放或结案。第二部分共包含37个变量，包括受害者特征和动机。第二部分的其他变量还包括工具性/表达性凶杀案指标、案件是否开放或已结案、逮捕类型、案件是否因逮捕而开放或结案、调查员数量、现场巡逻警员数量、目击者数量和结案的调查时间。第三部分共包含46个变量，包括主要/次要现场指标、现场类型、证据数量、现场总时间以及拍摄的图片数量。第三部分还包括测量是否发现16种特定类型证据的变量，以及为13种特定证据类型收集的证据项目数量。