We constantly hear about new technology that will help police officers to do their jobs.

Crimes with no witnesses can now be solved through the almost magical analysis of skin cells left on a door knob. Car-mounted cameras can scan license plates and find the cars that have been reported stolen.

But residents of Maine, Massachusetts and New Hampshire, motivated by the haunting image of 6-year-old boy who had been found dead, reminded us this week that there is no substitute for what can only be done by people who care.

Julianne McCrery, mother of the boy who died, is in custody today, charged with his murder, because of the most basic kind of community involvement: Somebody saw something and somebody said something.

Almost as soon as the police announced the discovery of an unidentified body, they also released a detailed description of a pickup truck, which a neighbor had seen earlier that day on a normally deserted South Berwick dirt road. That description was remembered by another civilian who saw a similar truck parked at a Chelmsford, Mass., rest area. Armed with the tip, police made an arrest.

We may never know what demons led McCrery to take her son’s life, a crime to which she has reportedly confessed. But we do know that because people paid attention and spoke up when it mattered, she did not get away with it. It’s tragic that no one saw or said something that could have prevented this horrific act in the first place.