We leave small clues about our lives all over the Internet like fingerprints.
Take Melvin Colon, who is facing charges of murder, along with weapons and narcotics-related crimes. The suspected New York gang member posted public photos on Facebook that showed him flashing gang signs but made private more incriminating posts, including references to past violent crimes and threats against others.
Unfortunately for Colon, one of his Facebook friends agreed to give police access to Colon's "private" information, and on August 10, a federal judge ruled Colon lost all claims to privacy when he shared those details with friends.
"Colon's legitimate expectation of privacy ended when he disseminated posts to his 'friends' because those 'friends' were free to use the information however they wanted -- including sharing it with the government," the judge wrote.
Leveraging Facebook is just one of many ways law enforcement officials are gleaning evidence from social media to help them solve crimes.
Police look at what information is public and sometimes create fake online identities to befriend suspects and view their private information. Authorities also can request private data directly from social networks with subpoenas or warrants, or make an emergency request for user information if they think there's an imminent threat of danger.
These techniques are slowly catching on across the country. According to a recent survey of 1,221 federal, state and local law enforcement who use social media, four out of five officials used social media to gather intelligence during investigations. Half said they checked social media at least once a week, and the majority said social media helps them solve crimes faster. The online survey was conducted by LexisNexis Risk Solutions and had a 2.8 percent margin of error.
The survey found that Facebook is the most fruitful social network for law enforcement, followed by YouTube.
Gathering public data
One pioneer in this emerging area is the city of Cincinnati, where police dismantled a local street gang and arrested 71 people in 2008 following a large nine-month investigation that used social media to identify key members. Collaborating with the University of Cincinnati's Institute of Crime Science, the police created databases of information scraped from social networks, existing police records and phone records, then used software to analyze the data and establish links between suspects.
As with most police departments, Cincinnati's social-media efforts began small, with a few officers checking online profiles on their downtime. Then police teamed up with the university and received training from social-media experts.
"A 22-year-old girl, who knew more about Facebook than Mark Zuckerberg did, taught us how to mine Facebook for info," said Capt. Daniel Gerard, who runs the department.
As they soon discovered, criminals were using social networks to blab about the crimes they were plotting, set up drug deals, brag about wrongdoings and even upload incriminating videos.
Criminals who can't resist bragging online are a boon to police and prosecutors across the country. In one 2008 case, Ronnie Tienda Jr. was convicted of a gang-related murder in Texas based largely on incriminating words and photos he had posted publicly on his MySpace pages.
Some "public" information takes a bit of maneuvering to find. Someone can have their Facebook settings as private as possible, but their friends or relatives might not be as savvy, allowing police to collect information by looking at what a suspect posts on their friends' public pages. Drug dealers have been known to post innocuous public updates that include location information so clients -- and unwittingly, law enforcement -- know where to find them, police said.
Police even have been using Facebook as a way to help victims identify suspects.
Going undercover on Facebook
A more controversial approach to getting information from social networks is going undercover online -- creating fake profiles to befriend suspects.
"We do have some covert accounts for targeted enforcements," said Cincinnati's Gerard.
Facebook, where almost 9 percent of accounts are believed to be fakes or duplicates, frowns on this practice, however.
"It just undermines the integrity of our whole service if we allow people to use false accounts," said Joe Sullivan, Facebook's chief security officer, in an interview with CNN last month. Creating a fake profile is against Facebook's terms of service, even for law enforcement. Sullivan said there is no context in which Facebook allows fake identities, and that it has a "large commitment" to finding and disabling false accounts.
While these fake accounts may violate a social network's rules, they are not illegal. And evidence collected in this way can still hold up in court.
"In other, nondigital circumstances, these types of practices have been upheld," said Hanni Fakhoury, a staff attorney at the Electronic Frontier Foundation, an Internet civil-liberties organization, in an email. "For example, the police oftentimes pose as young girls to capture people for soliciting a minor to engage in sexual activities. Or they pose as a potential drug buyer in order to arrest individuals on drug crimes."
The LexisNexis survey found most law enforcement officials have no qualms about creating fake profiles for investigations, with 83 percent saying they thought it was ethical.
Using proper channels