It used to be you needed a police radio scanner to know where the sirens were heading or why there was a bunch of patrol cars parked down the street.

All you need now is to follow someone on Twitter who listens to a police scanner and issues notes about what police, firefighters and other public safety personnel are doing.

Police agencies and others are using Twitter to broadcast details about manhunts, crime scene investigations and major traffic accidents as they're happening.

The Modesto Police Department's Twitter page has about 3,200 followers who receive updates on evolving major incidents and links to news releases about investigations.

"It's definitely another communication tool," said Modesto police spokesman Sgt. Rick Armendariz. "It's providing the public real-time information."

Tweets, however, can also hamper police work as news outlets and novice scanner listeners send alerts with unverified details of rapidly changing incidents.

Although some officials have concerns, they also recognize that as the popularity of this social networking site continues to grow, so will its capacity to deliver instant news.

It's growing use was evident during a two-week search for 4-year-old Juliani Cardenas. News media constantly tweeted information about the case, from the Amber Alert hours after his abduction to the recovery of the boy's body from the Delta-Mendota Canal.

Public information officers typically provide information to news outlets that in turn inform the public. But now, Armendariz can send a tweet, instantly communicating with the public himself. For example, he tweeted a suspect's description shortly after a bank robbery last month in west Modesto.

He said Twitter helps the department "to have more eyes on the street."

The department also has used Twitter to steer people away from major accidents, such as a fatal crash on McHenry Avenue on a busy weekday morning last month.

"We've used Twitter on incidents where we've had a large police presence," Armendariz said.

Twitter a 'valuable tool'

Tweeting about a yard-to-yard neighborhood search for a suspect can alert residents to stay indoors to ensure their safety. For example, Stanislaus County Sheriff's Department spokesman deputy Luke Schwartz used Twitter in December to notify residents of an incident in Hickman.

After a botched home-invasion robbery in a rural area, two of five suspects were missing. Schwartz sent tweets to keep people away from where the search was taking place.

"It's a valuable tool that allows us to get our message out," Schwartz said. "You're going to see a lot more law enforcement agencies get on board with social networking sites like Twitter and Facebook."

The California Highway Patrol has created a Twitter page for each of its divisions. But only the Southern Division in the Los Angeles area is tweeting, said CHP statewide spokeswoman Jaime Coffee.

She said she expects the CHP's use of the social networking site to grow.

"It's the direction things are heading," Coffee said. "It's where a lot of people get their information from."

During manhunts, police say, tweets with too much tactical information can leave officers dangerously exposed.

"(The suspect) might know we're close by," Armendariz said. "It can jeopardize investigations or risk the safety of victims, bystanders or the officers."

In these situations, he said, police can switch to other frequencies and use other tactics to "reduce our exposure and enhance our safety."

The Bee's Twitter page has more than 3,700 followers. On The Bee's Twitter feed @modbee, reporters or editors tweet basic details of what's heard over the radio scanner, like the general area of a crime or fire and the investigating agency. They follow up with authorities for further information.

Transforming the media

Carlos Rodriguez, chief editor for Central Valley Report, said he sometimes withholds information heard on the scanner. Earlier this week, he said he withheld some details of a police search for a suspect in northeast Modesto, fearing it could put the officers at risk.

"I don't think that's the smart, safe or fair thing to do," Rodriguez said.

Rodriguez used to shoot video footage for a daily television news show. Twitter transformed things about two years ago.

He said Twitter essentially ended the TV news show, which then morphed into a strictly Internet operation. Twitter, Facebook and YouTube allowed the three-person news operation to reach its audience more efficiently and at a lower cost.

"It's powerful," Rodriguez said. "I can go onto a (crime) scene, utilize something as small as my cell phone and send out information immediately."

Schwartz said Twitter has created an intense appetite for immediate response from police agencies that might have few details about a crime incident that is still evolving.

"They want information faster than we can gather it," said Schwartz.

Police radio traffic includes information that changes rapidly. Dispatchers initially give responding officers information reported by witnesses, victims or others at the scene.

"It's raw information," Armendariz said. "Oftentimes, what is initially reported is not what has occurred."

Rodriguez of Central Valley Report said he will immediately tweet the location of a shooting or a police pursuit in an effort to warn residents to stay inside or stay away. Those tweets can alert residents who might become crucial witnesses for police.

"(Twitter) is almost like a neighborhood watch online," Rodriguez said.

Finding proper balance

The balance between immediacy and accuracy is tough to find for news outlets tweeting, said Qingwen Dong, chairman of the communication department at the University of the Pacific in Stockton.

"This is the challenge. I understand how eager news reporters are to send out information," he said. "We need to double-check the information and the sources. We need to talk about the social responsibility of sending out this information to the public."

"They do not know what is involved in the (news gathering) process," Dong said. "They do not check and recheck."

News outlets must meet ethical standards to be accurate, Armendariz said, but others on Twitter might not be meeting those standards.

His message to Twitter followers: "Just consider the source."