When a Wilmington man in his early 20s overdosed on heroin the day after Christmas, local police Detective Pat Nally turned to his computer. He wanted to look at the deceased's Facebook and MySpace pages for possible clues about the source of the drug and who might have been using it with the man.
"People arrange to buy and sell drugs on Facebook; there's talk of what they may do and where they may go," said Nally. "We'd be foolish not to use it as an investigative tool."
The Wilmington investigator is not alone. In an informal survey of 14 departments in this area, officials in half of them said they use social networking websites such as Facebook and MySpace in detective work - particularly in investigations involving young people.
In Harvard, the police signed on to such sites about three years ago, after a woman was sexually assaulted and beaten by three men whom she met on MySpace and invited to her house. Police contacted MySpace and tracked the assailants using their online usernames and accounts, said Chief Edward Denmark.
Now even the chief has a Facebook page himself.
In a recent photo he used in his profile, Denmark appears as a singer from the 1970s with an Afro, long sideburns, and a flashy necklace. It's not him: Denmark says he changes the photo daily.
Harvard Police Officer Daniele Fortunato is also on Facebook. If you had searched for her on the site recently, you would have found a cat in a white-and-red Christmas hat stretching out on a bed (it's her profile photo), while Harvard police Sergeant James Babu appears as a smiling pig, with big ears and perfect white teeth.
Since the MySpace incident, the department has found that such websites can be useful to help identify suspects, Denmark said, by providing information about a particular person's contacts.
"We ask them if they know a certain person and [if] they tell us 'no' and we look on Facebook and see that they're friends, we know they're being untruthful," he explained.
In Nashua, police Sergeant Mike Carignan said Facebook helps police identify suspects by making it possible to "put a face to a name." He said the department uses such sites in investigations involving sexual predators, burglaries, drug dealers, and wanted people.
In Boxborough, Sergeant Warren Ryder said police were able to prevent underage drinking at a high school graduation party using information they obtained on Facebook. "They were talking about who was going to get the booze first," he said.
He said police also solved a vandalism case after someone posted a picture of the spray-painted graffiti on Facebook.
In Lowell, police Captain Randell Humphrey said Facebook can be useful in cases involving computer crimes, such as threats, as well as fraud and sex-related crimes, while Woburn even employs a detective whose responsibility is to monitor Facebook and MySpace.
At the state level, the Office of the Commissioner of Probations has an employee who checks the activity of juvenile probationers on Facebook, to see what mischief they may be planning, said Corea Holland, spokesman for the agency in Boston.
The Middlesex district attorney's office, meanwhile, uses the social networking site as one way to gather evidence. District Attorney Gerry Leone said both Facebook and MySpace have been useful in cases involving pornography and child enticement. In November, a Winchester Middle School teacher's aide was arraigned on child rape and pornography charges based on evidence the district attorney's office obtained from social networking websites.
"In light of the explosion of the Internet and the use of electronic communications, it's more important to us than ever," Leone said.
Marc Zwillinger, a Washington, D.C., lawyer who represents social networking sites, said requests from investigators to websites for information about individuals "are steadily increasing," and he's certainly seen subpoenas from the police as well. Law enforcement officials request access to information users provided when they registered for the site - such as their name, IP address, zip code - and sometimes want to look at their private message exchanges, Zwillinger said.
"We see a lot of it in sexual assault cases. They want to know what kind of messages were sent back and forth," he said.
In cases where one person argues the sex was consensual, while the other says it was rape, messages on social networking sites can shed light on what happened, he said.
So how do police do their detective work on Facebook?
Denmark said he would have no reservations about going undercover on Facebook - taking on a fake identity and tricking a suspect into accepting a police department employee as a friend, which would give police full access to the suspect's online profile.
"If the need ever arises, we're not against doing that," he said.
No special permission from a higher authority, such as the US attorney general's office, would be required, he said.
"It wouldn't be like a wiretap. It's no different than putting on a pizza guy uniform and knocking on the door," he said.
Leone said officers already engage in undercover conversations on Facebook if they have "a reasonable suspicion."
But some critics say this practice is against Facebook's rules - and unethical.
Facebook spokesman Simon Axten said that the site's rules forbid people from using fake names and that Facebook would not make an exception for police officers working undercover.
Jennifer Lynch, a lecturer at the law school of the University of California in Berkeley, said there are ethical issues involved when police pretend to be someone's friend to get access to their profile.
"If police is creating a fake profile and asking to be a friend, they are not going through the court" to obtain a search warrant, she said. "So you're losing the checks and balances that we value in our criminal justice system."
Kyle Bannon, 19, a Bedford, N.H.-based member of the Facebook group "Bedford cops need a life," agrees police working undercover on Facebook is akin to "searching without a warrant."
"It doesn't seem like the forefathers of our country would be too keen on that idea," he said.
The group has more than 200 members, mostly Bedford High School students who are frustrated with local police and use the site to share their stories about what they say were unfair speeding tickets and other incidents.
A similar Facebook group in Reading, Mass., has 63 members, and even features comic strips about students hijacking a police cruiser with a shotgun in the backseat, and a caricature of an officer with doughnuts falling out of his pockets. A recent post on the group's "wall" suggested that the students suspect the police department may have discovered the group.
"Being in this group is the stupidest idea," wrote a Reading Memorial High School student on Dec. 3. "The Reading cops know the names of all the people who are in it."
But Reading police Lieutenant Detective Richard Robbins said he does not believe his department uses Facebook.
Officials in several other departments also said they do not use Facebook, and some said they did not know what it is.
"Safebook? It's called Safebook?" asked Dunstable police Lieutenant James Dow. "I don't even know what it is."
The police dispatcher in Merrimack, N.H., asked: "Spacebook?"