Increasingly, prosecutors are relying on high-tech gadgets to give them an edge against bad guys who brazenly kill, stab and rob in the dead of night when witnesses are nowhere to be found.
Surveillance video, cellphone tracking, cellphone record investigations and ShotSpotter, a gunshot detection system, have all become important tools for prosecutors, allowing them to identify, track criminals’ whereabouts and build bulletproof cases, according to Bristol County District Attorney Thomas M. Quinn III and Plymouth County District Attorney Timothy Cruz.
In interviews, they raved about the value of these high-tech tools now at their disposal.
Front and center in prosecutors’ toolbox is surveillance video, which is available from public and private sources and actively sought by crime scene investigators, they said.
‘‘It’s a game changer,’’ Quinn said, comparing video surveillance to the instant replay of a suspect’s criminal acts.
Quinn and Cruz said it has become such an important feature for them that when they are responding to violent crimes, police and prosecutors knock on doors and approach neighbors and businesses, asking if they have security systems.
‘‘That’s one of the first things they’re looking for — videotape, video surveillance,’’ Quinn said.
In the past five years, the prevalence of surveillance video among private homeowners and commercial establishments has exploded, making it well worth a smart detective’s time to pound the pavement in search of private security systems, they said.
‘‘Now it’s everywhere. It’s so pervasive. Everyone is on camera,’’ said Wareham Police Chief Kevin Walsh. ‘‘It’s usually a part of every investigation where in the past it was a luxury.
‘‘If it’s not on surveillance camera, it’s probably on someone’s phone,’’ he said.
In the height of irony, some suspects learn after the fact they have been implicated in a crime by their own home security systems.
Prosecutors have video in two of New Bedford’s three murders this year, according to Detective Capt. Steven Vicente, public information officer for the New Bedford Police Department, and comments by assistant district attorneys at criminal proceedings in New Bedford District Court.
In the investigation into the Aug. 2 slaying of 24-year-old Jeffrey Sylvia Jr., police have video from the home of the suspected shooter, 22-year-old Michael Sousa, who is charged with murder and armed robbery, prosecutors have said.
And in the only homicide in New Bedford this year where there is no surveillance video — the killing of 19-year-old Marcelo Jean Francois on June 11 in the West End’s Harrington Park — the City of New Bedford has since installed cameras, equipped with night vision capabilities and high resolution.
In Brockton, video from a car wash in Brockton proved instrumental in solving a bar shooting there, Cruz said.
While investigating a report from the hospital that a man was being treated for a gunshot wound, police found a bullet hole in the door of the bar — but only reluctant witnesses inside the establishment and no shell casings lying on the street, he said.
It was not until police pulled the video from the car wash across the street that things began to make sense, he said.
The video showed members of two groups fighting and one firing a gunshot through the bar’s door, wounding a man, Cruz said. That footage was followed by a frantic scene where people were running out of the bar and carrying out an injured patron with others bending down to pick up shell casings on the ground.
‘‘But for that video, no one would have known what happened,’’ Cruz said.
‘‘You want to show everything you can. They do a good job of tying things up,’’ he said, speaking generally about surveillance video.
‘‘It may be the difference between finding someone guilty or not guilty,’’ Cruz said. ‘‘It’s that cutting edge stuff, coupled with good-old fashioned police work that makes a difference.’’
In Marco Shane Ramos’ murder trial, which ended Friday, prosecutors said video from Ro-Art Liquors, 23 Rodney French Blvd., New Bedford, showed him stabbing the victim, 22-year-old Alex Silva, on July 31, 2014.
According to court documents, Ramos grabs at Silva, pushes him off the bike and ‘‘Mr. Silva is seen reeling backwards.’’ Minutes later, the victim, bleeding from a chest wound, appears at the South End Station on Cove Street.
Jurors found Ramos, 27, of New Bedford guilty of first-degree murder Thursday in Fall River Superior Court and he was given the automatic sentence for a first-degree murder conviction of life in prison with no chance of parole on Friday.
Neither the Bristol nor Plymouth County DA offices keeps statistics on the impact high-tech evidence, such as surveillance video, has on their cases. For example, they cannot say whether it has resulted in more pleas, eliminating some trials all together.
Undoubtedly, though, video evidence strengthens their cases, they said.
A video, coupled with the time and date affixed to the footage, were important pieces of evidence in the trial of former New England Patriot Aaron Hernandez, convicted of first-degree murder in the shooting death of Odin Lloyd. Video was also valuable in the case of Joshua Silva, found guilty of first-degree murder in the 2013 slaying of retired school teacher Joyce N. Howland in her Fairhaven home.
Quinn said that in both cases, the video established a timeline that helped to close the net around Hernandez and Silva.
With Silva, the video gave jurors something they could ‘‘visualize,’’ he said. They saw Silva driving his employer’s Fairhaven Lumber truck past the Stop & Shop Supermarket on the day Howland was killed and then later heading back past the supermarket.
‘‘It’s powerful when you have the suspect on video at critical times,’’ Quinn said.
‘‘It really helped us establish a timeline of where the suspect was after the homicide itself,’’ Sgt. Kevin Kobza, public information officer of the Fairhaven Police Department, said.
Also, a video showing Silva throwing the label from a prescription bottle belonging to Howland behind the Pasta House Restaurant was ‘‘a key piece of linking evidence.’’
In the Hernandez trial, the video was augmented with cellphone evidence, according to Quinn.
Jurors saw Hernandez on video at many different times — leaving his North Attleboro home; stopping at a gas station; outside Lloyd’s home in Boston; and at the Weston toll plaza, he said. It also showed his girlfriend, Shayanna Jenkins, putting something into a box truck.
‘‘That was critical in that case,’’ Quinn said, adding the surveillance they had in the case included some from Hernandez’s own residence.
The Bristol DA said five years ago in a homicide in Fall River his office had surveillance video that captured the defendant at the scene of the murder.
‘‘Objectively, it is at the very least, helpful,’’ in terms of its impact on a jury, he said. ‘‘I think it’s strong evidence that can cement in their minds proof of the case.
For instance, it can show the time a suspect enters a building and the time he or she leaves, he said.
‘‘It can only help our cases because it’s tangible, direct evidence,’’ he said. ‘‘It presents a strong chronology. It’s a direct link.’’
The cellphone tracking of a suspect or a victim’s phone has become a significant part of every murder investigation, Quinn said.
‘‘It leads you to individuals you would not ordinarily know about,’’ he said. ‘‘I think that it has solved cases that would not normally be solved.’’
It can also lead investigators to people they knew nothing about, he said.
New Bedford, Fall River and Brockton all have ShotSpotter, the acoustic gunshot system that tells police dispatchers instantly when gunshots have been fired within a covered area.
Cruz said the system ensures ‘‘quick response’’ by police and is a fail-safe mechanism in the event people do not call authorities when they hear shots and it gives police accurate information to adjust their list of hotspots in a community.
Brockton officials are also in the process of expanding the area covered by Shotspotter in that city, Cruz said.
In New Bedford, ShotSpotter, is also saving lives because emergency medical personnel are getting aid to shooting victims quicker, officials have said.
Jack Levin, a criminologist and professor emeritus at Northeastern University, said high-tech gadgets are extremely valuable to law enforcement, yet they come at the expense of people’s civil liberties.
‘‘High-tech cameras were responsible in England for bringing terrorists to justice and have prevented terrorists’ attacks,’’ he said.
But there has to be a balance between public safety concerns and privacy and that invariably sparks debate on ‘‘Where is the line?,’’ Levin said.
‘‘How much freedom are we willing to give up to be safe?,”’’ he said.
Personally speaking, Levin said high-tech gadgets are ‘‘terrific tools,’’ and he favors their use to prevent violence and prosecute criminals. ‘‘They are there if and when there are criminal acts,’’ he said,
But while technology gives law enforcement an edge, cops say nothing beats some good, dogged police work.
‘‘It will never replace human intelligence,’’ Kobza said. ‘‘Does it help? Absolutely. Is it the be-all, end-all? No.
‘‘You are still going to need people to interview witnesses, follow-up on people,’’ he said.