If a criminal steals your gun and shoots someone with it, you are not liable for the death. That is basic common sense. It also is the law, as upheld by the U.S. Court of Appeals in Boston on Friday in a case brought by a mother whose son was murdered in New Hampshire.

The grief of Gail Jones, the Halifax, Mass., mother who brought the case, must have been overwhelming. Her son Gary was one of the three innocent victims murdered in a Conway military surplus store in 2007. He just happened to walk into the store as Michael Woodbury, a fugitive wanted in five states, was walking out, having just shot the manager in the back of the head.

Woodbury entered the store “thinking the most heinous, evil thoughts,” he told investigators. He wanted to steal a car he saw in the parking lot. He thought the manager, James Walker, was armed, and when Walker bent down after the two men had been talking, “I capped him. I shot him in the back of the head,” Woodbury said. Moments later, Jones and a friend, William Jones, entered the store. Woodbury said he killed them because he thought they would try to arrest him.

A criminal with a history of mental illness, Woodbury obtained the .22 caliber handgun he used that day by stealing it from his grandfather’s Wentworth Location hunting camp. The grandfather, Lawrence Secord of Maine, kept the unloaded gun hidden inside his locked camp. Woodbury broke into the unoccupied camp and stole it. In her lawsuit, Gail Jones claimed that Secord was responsible for her son’s death through his failure to properly secure his handgun.

In rejecting Jones’ claim, the court on Friday cited the “fundamental unfairness” of holding Secord responsible for Woodbury’s criminal acts. Only one person was responsible: Woodbury, who said at his sentencing, “I’m pleading guilty because I am guilty.”

We cannot imagine the anguish and suffering Gail Jones and the other victims’ parents have gone through since that day. Their pain was compounded by the fact that Woodbury was not eligible for the death penalty and was sentenced to life in prison. Merrimack County Superior Court Judge Edward Fitzgerald told the victims’ families at sentencing, “I pray that you may have some peace and closure. I cannot do justice.”

He could not. Nor could the Jones family by trying to hold Woodbury’s grandfather responsible. The responsibility was Woodbury’s alone. That he was not fully punished for his crimes is maddeningly frustrating, but no justification for transferring the guilt to someone else.