Twenty months ago, James Lewis was appointed chief of the New Haven police department for the remainder of former Chief Francisco Ortiz, Jr.’s four-year term. Friday was Chief Lewis’ last day on the job.

Everyone who lives or works in New Haven owes Chief Lewis, the two assistant chiefs he brought with him, Roy Brown and Kenneth Gillespie, and the other officers of the department a profound debt of gratitude. He and they have transformed the department to a much greater extent than anyone imagined possible 20 months ago.

Lewis was appointed several months after the city was rocked by the arrest of Lt. William White, a 39-year veteran of the department and longtime head of its narcotics unit, on federal charges of bribery conspiracy and theft of government funds. Another detective was also arrested for theft of government funds. The charges resulted from payments received from city bail bondsmen to locate and arrest fugitives as well as instances in which the detectives kept money found in drug-related searches.

Those arrests were only the tip of the iceberg. The city brought in the Washington-based Police Executive Review Forum to review of the department’s policies. Shortly, after Chief Lewis had taken office, PERF delivered a scathing indictment of the department.

Charged with understanding how such egregious action could have been taken by White and others, PERF found that there were no formal policies and procedures for the narcotics unit. Instead, supervisors and officers created their own policies and practices with respect to informants, targets and priorities, use of funds and seizure of drugs and money. There were no background checks, financial reviews of officers or periodic audits and inspections of the unit.

But the report was not limited to the narcotics unit; it touched on every aspect of policing in New Haven. PERF found that not only was the NHPD missing an overall strategy for combating crime, but it also had no formal system of evaluating performance or of job rotation and lacked up-to-date written directives, policies and procedures. In addition, it was seriously deficient in its collection and reporting of crime data and for years had failed to report crime data to the FBI. PERF could not even determine clearance rates for crimes other than homicides.

Moreover, the department had serious staffing problems. There had been no promotions to captain for nearly a decade and until shortly before the report was issued, none to lieutenant to sergeant. As a result, NHPD lacked sufficient personnel at the senior management level. Vacancies had been largely filled on a temporary or acting basis.

PERF also found that detectives lacked any formal training, computers and a system for tracking cases. Although it had a forensics unit, it did not employ and professionally trained forensic scientists.

And while there was a system by which citizens could complain about officers’ conduct, PERF found that many complaints weren’t investigated fully or at all.

No one who read the preliminary PERF report in the fall of 2007 imagined that Chief Lewis and his team would be able to implement all or even most of its 57 recommendations in the next 20 months. Indeed, those who participated in the community forums held to discuss the report urged PERF to identify priorities and establish benchmarks as well as criteria by which the city could determine whether the recommendations had been implemented.

Yet 20 months later, most of the recommendations have been implemented. Policies and procedures in virtually every area of policing have been updated and, where needed, changed. The senior management ranks have been filled with captains and lieutenants. A new and more aggressive strategy for fighting crime — Targeted Activity Policing — has been developed and implemented with much success. The drug unit has been reconstituted with new procedures, controls and officers who have been carefully screened and extensively trained. Special emphasis, including the aggressive enforcement of traffic laws and the use of periodic gun buyback programs, has been directed at getting guns off the streets and reducing the numbers of shootings.

The results are evident in the crime statistics.

Admittedly, some officers objected to Lewis’ stern discipline. And some members of the community criticized his aggressive approach to policing and accused him of abandoning community policing, as the News did last week (“Outgoing chief reflects,” Feb. 26). Such claims miss the big picture of what was wrong, what needed to change and what has changed over the past 20 months.

Crime is still much too high in New Haven. But the police are better prepared today than they were 20 months ago to prevent crime and solve the crimes that occur.

Thank you, Chief Lewis. You will be missed.

David Cameron is a professor of political science, a member of the East Rock Management Team and has served on the Civilian Review Board.