Snapchat has a filter that allows users to record their speed of travel, and she wanted to see how fast she could go. So McGee accelerated, then accelerated some more, reaching 113 miles per hour (181kmph) on a suburban road outside Atlanta where the speed limit is 55.
She didn't see Maynard Wentworth, an Uber driver just starting his shift that night, until it was too late. She hit him at 107 miles per hour (172.2kmph).
Wentworth suffered a traumatic brain injury and was hospitalized for months.
Now he and his wife are suing McGee - and Snapchat - for negligence. The narrative of that night is outlined in a civil complaint filed in Spalding County court last week, which alleges that Snapchat was equally responsible for the cause of the crash because the company did not delete the miles per hour filter from the app after it was cited in similar accidents prior to the September 2015 crash.
The complaint and a statement from Wentworth's lawyer, Michael L. Neff, explain that night like this: McGee was driving several of her friends home from work at a local restaurant in Hampton, Ga., a suburb of Atlanta. One of the friends was pregnant, according to the statement from Neff's office. Over the pregnant passenger's objections, McGee urged the Mercedes faster and faster.
She argued, according to the statement, that she was trying to get the car to 100 miles per hour (160.9kmph) so she could post it on Snapchat. McGee's passengers saw the controversial filter hit 113 miles per hour. The teen was just about to post the Snapchat, the statement says, when she crashed into Wentworth's Mitsubishi.
The collision caused Wentworth "permanent brain damage," the complaint says, rendering him unable to work and causing him to lose 50 pounds since the wreck.
McGee hit her head on the windshield of the Mercedes - then Snapchatted a photo of herself backboarded, in a neck brace, blood trickling down her forehead, according to the statement. The caption on the Snapchat read: "Lucky to be alive."
Wentworth's lawyers argue that McGee's behavior could have been prevented had Snapchat taken greater precautions with its miles per hour filter.
"On and before September 10, 2015, Snapchat knew that wrecks had occurred due to the use of Snapchat's app while driving at high speed," the complaint says. "Despite Snapchat's actual knowledge of the danger from using its product's speed filter while driving at excessive speeds, Snapchat did not remove or restrict access to the speed filter."
A Snapchat spokesman told CNN that he could not speak about pending lawsuits, but added that a warning not to Snapchat while driving has always been included in the app.
© 2016 The Washington Post
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