The Middlesex County Chiefs of Police Association announced the signing last week of the Massachusetts Interagency Mutual Aid Agreement, authorized by state law, which will empowers on-duty police officers in one jurisdiction to respond to public safety emergencies in other participating jurisdictions in certain circumstances.

The historic agreement, to date signed by 51 of the 54 communities in Middlesex County, as well as Wellesley, Lynnfield and Saugus, establishes a strategic working partnership among the police departments that will provide community benefits in both day-to-day life and during a major incident.

The crux of the agreement is twofold: First, police chiefs now have a formal method of requesting immediate mutual-aid assistance from neighboring communities during a critical incident or crime in progress; second, an on-duty police officer, who may be traveling to court for the day or transporting a prisoner, can act if they observe a drunk driver or other unlawful behavior while traveling through another community.

“Police officers are expected to always be police officers, and they should never have to put themselves or others in danger by hastily rushing to stop a reckless driver or wanted felon before the town line,” Weston Police Chief Steven Shaw, president of the Middlesex County Chiefs of Police Association, said. “Crime doesn’t stop at the border, and this agreement will help ensure that criminals can’t escape the law by escaping one community.”

The agreement is the product of more than a year of research and work by a special subcommittee of the Middlesex County Chiefs of Police Association, led by Arlington Police Chief Frederick Ryan. The work stemmed from two Supreme Judicial Court Decisions: Commonwealth v. LeBlanc (1990) and Commonwealth v. Bartlett (2013).

In the LeBLanc case, a drunk driver’s case was thrown out because a Natick police officer followed the driver, who had been speeding and ran a red light, over the border into Framingham. The case left police with little recourse under the law at the time.

The Bartlett case, however, held that police departments could establish interagency mutual aid agreements, extending policing powers to neighboring communities.  Middlesex is the first county in Massachusetts to sign such an agreement.

The agreement also covers nearly every community that the 2014 Boston Marathon will pass through. Major events like the marathon attacks last year and the security efforts for the marathon this year underscore the need for cooperation among different law-enforcement organizations.

“Major events in Massachusetts and elsewhere have highlighted the need for police departments to work together more effectively, and these events have shown that we are indeed more effective when we work together,” Bedford Police Chief Robert Bongiorno, secretary of the Middlesex County Chiefs of Police Association, said.

“Working together, across invisible boundaries, is a real step in the right direction,” Belmont Police Chief Richard McLaughlin, treasurer of the Association, said. “I’m proud to sign this agreement. It will make the community safer, and it will keep police officers safe.”

The agreement allows municipal police chiefs to retain command and control of incidents in their communities. It also requires police officers to notify the commanding officer of the community when they enter to conduct policing activities. The officers will either be requested as mutual aid from the neighboring community or they may “self activate” when they observe or become aware of a violation of the law across the border.  The on-duty police officer may exercise his or her police powers within any community covered under the agreement.

Of the three remaining departments in Middlesex County, the chiefs of the Waltham and Winchester police departments have submitted the agreement to their municipal government for approval. Cambridge has not signed the agreement at this time.