The research examined the presentation in 3 Crown Courts and 4 Magistrates' Courts by 232 officers from the London Metropolitan Police and the Hampshire Constabulary. Assessments of police performance were elicited from judges, jurors, prosecuting attorneys, defense attorneys, and police officers themselves, using a combination of structured questionnaires and interviews. In addition, 26 police officers were observed giving evidence in each of the 7 courts. Results revealed generally satisfactory but variable performance. However, both the responses from participant groups and the observations revealed some commonly perceived deficiencies that occurred consistently. Officers were often nervous when giving testimony; this attitude adversely affected their general demeanor. In addition, officers were widely perceived to rely excessively on their written notes. Moreover, some officers appeared to have an insufficient grasp of court procedures and the rules of evidence. Furthermore, officers' performance under cross-examination was one of the least satisfactory aspects of their performance as witnesses. The most significant issue was the dependence of the officer's performance as a witness on the standard of prior processes, including the investigation, reports, and preparation. Findings indicated several ways to improve the standard of presentation of evidence. Recommended actions include changes in training, supervision, the handling of practicalities, and the provision of a guide to good practice. Findings indicated that most officers make a good impression on the court but that several weaknesses should be addressed. Tables, appended methodological information and tables, and 2 references