Three young men got into a car in Walworth County, Wis., in May 2017. They were set on driving at rapid speeds down a long, cornfield-lined road — and sharing their escapade on social media. As the 17-year-old behind the wheel accelerated to 123 miles per hour, one of the passengers opened Snapchat. His parents say their son wanted to capture the experience using an app feature — the controversial «speed filter» — that documents real-life speed, hoping for engagement and attention from followers on the messaging app. It was one of the last things the trio did before the vehicle ran off the road and crashed into a tree, killing all of them. Was Snapchat partially to blame? The boys’ parents think so. And, in a surprise decision on Tuesday, a federal appeals court ordered that the parents should have the right to sue Snap.