If a store sells ammunition to an underage person who uses the bullets to kill someone, is the retailer responsible?

Not necessarily, according to the Mississippi Supreme Court. The court ruled 5-4 this week in favour of Wal-Mart.

The lawsuit was filed by the relatives of Robert Williams, who was shot and killed by his girlfriend's son in 2006. The son, Xavier Zurndell Moore, was 20 years old at the time, and shot Williams with a pistol cartridge purchased at the Wal-Mart in Indianola.

Federal law requires that a person be 21 to buy pistol ammunition. The lawsuit claimed that a store employee allowed Moore to obtain the ammunition through a straw purchase, meaning the worker sold it to Moore's 21-year-old friend, while knowing Moore would be the recipient.

There was conflicting testimony about how the ammunition was purchased. The employee said Moore asked if the store had .45-calibre ammunition and walked away when asked which brand he wanted. Moore's friend came back and bought the ammunition, though the employee allegedly saw Moore give his friend the money, according to the court record.

Moore told a different version of how he purchased the ammunition. Moore said he told the employee he didn't have his identification and asked if friend could buy the ammunition, which he said the clerk allowed.

The next day, Moore went out with his girlfriend and they drank vodka together. By early morning, they were back at his house and in his room with the door locked. Williams banged on the door and demanded a fan Moore had borrowed. Moore claimed Williams had been abusive before so he shot through the door in an attempt to scare him, but accidentally shot him in the head, according to the court record.

Moore said he meant to shoot up and at angle, but may not have because of the alcohol.

"I guess my vision was a little off. I shot a little bit lower than I thought," he said later, according to court records.

Moore pleaded guilty to manslaughter.

Wal-Mart spokesman Randy Hargrove said the Bentonville, Ark.-based company believes the court "reached the correct decision."

"We are sorry about Mr. Williams' death and extend our condolences to his family and friends," Hargrove said. "We are committed to selling ammunition responsibly and work diligently to make sure we follow all state and federal laws."

A lawyer representing Williams' family didn't immediately respond to a message.

Circuit Judge Ashley Hines granted summary judgment in the case, ruling in favour of Wal-Mart based on a Mississippi case from 1979.

In that case, Robinson v. Howard Brothers of Jackson, a man sued Howard Brothers after the store sold a pistol and ammunition to a minor, who used the gun to kill the man's wife. The court sided with the store based on the finding that it was not "within the realm of reasonable foreseeability" that the minor would use the gun to kill someone.

Wal-Mart made a similar argument.

That's not to say that a store can't be held liable in Mississippi for selling weapons or ammunition to someone who isn't authorized to buy them. A Mississippi court ruled in favour of a plaintiff in a 1986 lawsuit. In that case, a schizophrenic minor who was drinking whiskey and high on drugs asked to see a gun and ammunition, then loaded the gun and took a hostage.

The court ruled in favour of the hostage in a lawsuit "due to the minor's severely impaired state at the time of the purchase, combined with the lax, inattentive conduct" of the store.

In the Wal-Mart case, a majority of the Mississippi Supreme Court found that there was little evidence to prove that Wal-Mart knew Moore was under age.

"Further, nothing in the record suggests that, at the time of purchase, Wal-Mart had any reason to believe that Moore would commit a criminal act," the court ruled.

In a dissent, Justice Jess Dickinson said he was alarmed the majority's conclusion found that a minor's reckless use of a handgun was unforeseeable.

"I find it even more alarming that, in order to get there, the majority presumes to evaluate and weigh the facts," he wrote. "Does the majority suggest that Wal-Mart would be insulated from liability if the age of the minor in this case had been 10? What about 12?"

AP