But in scores of instructional memos over the last three years, the New York Police Department has been moving to standardize detective work and codify crime-solving tactics that had mostly existed as an oral tradition in the squad rooms of precinct station houses.
Some of the memos detail investigative methods, like how to surreptitiously take a DNA sample from a suspect during an interrogation or while trailing him on the street.
Other memos provide only general guidance, like Memo 24 of 2011, which concerns videotaping interrogations. It authorizes detectives to use “lawful deception, deceit, trickery, etc.” when seeking a confession. And offensive language — ordinarily against department protocol — is permissible for “facilitating communication or obtaining information.”
Sometimes, the instructions go further, spelling out the very words detectives must say. Memo 31 of 2011, a 61-step mini-manual on police lineups, orders detectives to ask verbatim: “Did you recognize anyone in the lineup? If so, what is the number of the person that you recognize? From where do you recognize that person?”
Because witnesses frequently offer uncertain answers — “I think it is No. 3,” for example — the memo instructs detectives to avoid a basic error: asking witnesses to gauge their confidence on a scale of 1 to 10. (Anything less than a 10 invites doubt from jurors at a trial.)
The memos are the handiwork of the chief of detectives, Phil T. Pulaski, who oversees some 2,200 detectives from the 13th floor of Police Headquarters, a rust-colored fortress behind the Municipal Building. While his predecessors issued occasional memos, Chief Pulaski is more prolific: he has generated some 85 step-by-step instructional memos since becoming chief in 2009.
Taken together, his writings are rapidly bringing detectives under greater supervision, and changing the freewheeling culture of the detective bureau.
Through a spokesman, Chief Pulaski declined interview requests.
But Paul J. Browne, the Police Department’s chief spokesman, said the memos bolstered accountability and ensured that police procedures were “applied as consistently as possible.”
Various protocols, like the one for lineups, “can’t be left to word of mouth, particularly as laws and forensics change,” Mr. Browne wrote in an e-mail. “Chief Pulaski understands this perhaps better than any of his predecessors.”
The memos underscore the changing nature of investigative work. Cases that once depended solely on the ability of detectives to elicit information from witnesses and suspects are now routinely bolstered by DNA evidence, video footage and cellphone records. Many of the memos created new protocols for gathering physical and electronic evidence. One memo offers suggestions for using the department’s 398 license plate readers. Another explains how to incorporate facial identification software into investigations.
The memos also recalibrate detective work in a city safe enough that a Manhattan South Homicide detective is often assigned lesser investigations while waiting weeks for the next murder case. A series of memos from September 2012, for instance, provided step-by-step instructions for investigating cellphone thefts.
In one of the memos, Step 10 advises, “Determine if stolen cellphone has ‘locator/tracking’ capability.” The memo identifies several: Find My iPhone, Google Latitude, Lookout, SmrtGuard, Mobile Defense.
In interviews, several detectives lamented that the balance of their days was shifting toward rote undertakings, like retrieving surveillance tapes from crime scenes; some detectives crisscross the city to different stores where stolen credit cards have been used in search of footage. Less time, they say, is devoted to pounding the pavement on bigger cases, of which there are fewer. Their complaints over some of the memos have led Chief Pulaski to meet regularly with representatives of the detectives’ union.
Some detectives describe a growing reliance on a checklist approach to investigations in recent years.
“When I first started, there were more homicides, more shootings and more detectives, and you didn’t sweat the small stuff,” said the novelist Edward W. Conlon, who spent a decade as a detective until retiring in 2011 from a squad in the Bronx. “There are now a lot less detectives, and constant sweat over small stuff.”
The precinct detective squads, usually occupying the second floors of police station houses, have long had a culture independent — even at odds with — the rest of the department. Until the second term of Mayor Michael R. Bloomberg, detectives still had permission to drink beer or wine on their breaks. Back in the squad room, they still tapped out reports on typewriters in carbon triplicate.
Over generations, detectives grew accustomed to an autonomy that their uniformed colleagues lost long ago when radios were first installed in patrol cars, making officers instantly accountable for their whereabouts, the police historian Thomas A. Reppetto, said.
Detectives now fall under similar scrutiny.
One memo, for example, is meant to stop an old practice: detectives, when signing in on the squad room ledger, sometimes skip a line to leave space for a tardy colleague to use. Detectives are now sometimes required to report to a patrol sergeant before starting their shifts, which many veteran detectives consider an indignity.
Detectives also sign the ledger whenever they leave on a case; a new memo requires audits of the ledger to confirm it matches the detectives’ other paperwork.
“There is a way to handle professional investigators and you don’t treat them like kids,” said a former homicide detective commander, Vernon J. Geberth, who criticized many of Chief Pulaski’s mandates as “encumbering the detectives’ mission.”
Chief Pulaski, a lawyer and engineer by training, has mentioned his intention to use the memos as the basis for a larger guide about detective work.
Robert J. Masters, a high-ranking prosecutor in Queens who attended law school with Chief Pulaski, said that the memos were a way to “formalize and codify” the informal detective lessons traditionally taught by “the experienced guy at the next desk.”
“What he’s trying to do is not discourage intuition or instinct, but to encourage good practices,” Mr. Masters added.