Prosecutors say two men murdered innocent 16-year-old during Dorchester gang feud

 Sheldon Mattis was led into Suffolk Superior Court where he was met by his defense attorney, Kelli Porges.
Sheldon Mattis was led into Suffolk Superior Court where he was met by his defense attorney, Kelli Porges.
Wendy Maeda/Globe Staff

Prosecutors today said two Boston men are jointly responsible for the murder of Jaivon Blake, a Dorchester teen with no ties to street gangs who was murdered because of a feud between two gangs in the Genvea-Bowdoin neighborhood in 2011.

In opening statements in the first degree murder trial of Sheldon Mattis and Nyasani Watt, Suffolk Assistant District Attorney Gregory Henning said Blake was gunned down on Geneva Avenue because his killers were trying to send a “deadly message” to their rivals.

“That message was about their toughness and their turf,” Henning said during his opening statement in Suffolk Superior Court. Henning said Blake, who wrote poetry and dreamed of being a professional basketball player, was not a member of any gang.

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The prosecutor alleged that the two defendants, both of whom are now 20 years old, targeted Blake because he was with a 14-year-old boy who happened to live on Everton Street, the territory of their gang rival.

Nyasani Watt (Wendy Maeda/Globe Staff)

On Sept. 25, 2011, Henning said in court, Mattis helped Watt conceal a .40-caliber semi-automatic handgun and patted him on the back just before Watt rode on his bike to Geneva Avenue to shoot Blake and the boy.

The 14-year-old was shot in the neck and shoulder and managed to run away, but Blake was shot through his spinal cord and collapsed to the ground, partially paralyzed and gasping for air, Henning said.

Blake’s brother rushed to the scene to find his sibling struggling to stay alive as he was placed in an ambulance. Blake died two hours later on the operating table at Boston Medical Center.

But Watt’s lawyer, veteran Boston criminal defense attorney Willie Davis, said that prosecutors have no witnesses who can identify his client as the shooter.

“They’re wrong,” Davis told the jury in his opening statement. “It will be up to you to tell them they’re wrong.”

In her opening statement, Mattis’s lawyer, Kelli Porges, acknowledged said that her client was close to Watt and had spent some time at the house where prosecutors allege gang members often gathered.

But, Porges said, that is not enough to convict him of first-degree murder.

She said prosecution witnesses will give inconsistent and contradictory statements about the incident that cost Blake his life.

“If you think one of the things they’re telling isn’t true, how do you accept anything they’re telling you?” she asked.

The 2011 homicide had frightening similarities to a 2010 killing in the Bowdoin-Geneva section of Dorchester, where 14-year-old Nicholas Fomby-Davis was shot to death by two gang members who mistook him for a rival. Joshua Fernandes, 19, and Crisostomo Lopes, 23, were convicted for the killing in 2012.

The trial, before Superior Court Judge Christine Roach, is ongoing.