DOVER, Del. — Delaware’s Supreme Court has upheld the conspiracy conviction of a teenage girl in a school bathroom attack that left a 16-year-old classmate dead.

In an order dated Tuesday, the court rejected the girl’s arguments that there was insufficient evidence to convict her in the April 2016 attack that left Amy Joyner-Francis dead.

The ruling came after the Supreme Court last month overturned a codefendant’s conviction for criminally negligent homicide for her role in the attack, while upholding her conspiracy conviction. In that ruling, the Supreme Court said no reasonable fact-finder could have found that the girl acted with criminal negligence. Even if she did, the justices said, it would be unjust to blame her for Joyner-Francis’ death given how unforeseeable it was that the fight would lead to a young teen dying of cardiac arrest.

An autopsy found that Joyner-Francis, who had a rare, undetected, heart condition, died of sudden cardiac death, aggravated by physical and emotional stress from the fight at Howard High School of Technology in Wilmington.

Cellphone video of the attack, which gained national attention, shows Joyner-Francis struggling to fight back and escape as she is repeatedly hit and kicked in the head while her assailant holds on to her hair.

Three girls were charged in the incident. Two were convicted, while the third was acquitted on a conspiracy charge. The Associated Press has not published their names because they were tried as juveniles. The Supreme Court in its rulings has referred to the defendants using pseudonyms.

The defendant, identified in Tuesday’s ruling under the pseudonym Zachary Schaffer, argued that Joyner-Francis was a “mutual combatant” in a fight between two willing parties, and that she thus could not be convicted of conspiracy to commit assault.

“Even if Schaffer’s theory has merit — a question on which we express no opinion — it had little evidentiary support,” Justice Gary Traynor wrote on behalf of a three-judge panel.

The girl also claimed that a Family Court judge who presided over a non-jury trial erred in allowing prosecutors to introduce two Snapchat videos as evidence without adequate authentication.

One of the videos, posted the day before the attack, shows Joyner-Francis talking to her assailant in the bathroom, purportedly to try to defuse the situation. The posting notes that the girl later convicted of homicide was “bouta fight her,” followed by several emojis indicating that a person was laughing so hard she was crying.

The other video bore a caption that read, “We gonna get her. She’s scared.”

Two witnesses testified that they had seen one or both videos posted to Schaffer’s account.

Schaffer pointed out that the witnesses could not remember exactly when they watched the videos. She also suggested that the videos could have been manipulated after they had been posted to her account to add the captions.

Pointing to the testimony of Schaffer’s two classmates, the justices rejected those arguments, saying the Family Court did not err in allowing the videos into evidence.

The Supreme Court also rejected arguments that Schaffer’s rights were violated because investigators were unable to recover an iPad issued by the school to Francis. Schaffer suggested the device may have contained information indicating that Joyner-Francis was willing to fight.

While detectives were unable to find the iPad, the justices noted that evidence the state was able to obtain of conversations Joyner-Francis had with a friend the day before the attack gave no indication that she had been willing to fight.

Prosecutors traced the conflict to an online group chat the day before the attack, when Joyner-Francis had offered advice to a friend about a problem involving a boy, telling her friend to “just be careful.” Joyner-Francis warned that someone might “switch up,” or betray another person. A police detective said the assailant thought Joyner-Francis was talking about her as the possible traitor.

The family of Joyner-Francis filed a lawsuit last week against the school district and the two girls convicted in the case.