PARK CITY, Utah (AP) — Skiers have likely noticed signs at mountain resorts across the country saying, “Know the code.” They refer to universal rules of conduct that apply to people who partake in inherently risky snow sports that involve navigating down crowded slopes, often at high speeds.

But whether they actually understand the code is another question. For those unfamiliar with skiing and snowboarding, it’s likely something they’ve never heard of.

That’s all changing as actor Gwyneth Paltrow’s highly publicized ski collision trial is live-streamed from the courtroom. The actor-turned-lifestyle-influencer was accused of crashing into a fellow skier during a 2016 family trip to the upscale, skiers-only Deer Valley Resort in Utah. The celebrity trial is on day six and expected to conclude Thursday.

For a week, the trial has shone a spotlight on the unspoken rules that govern behavior on the slopes. Testimony has repeatedly touched on skier’s etiquette — especially sharing contact information after a collision, and ski turn radiuses — in the most high-profile ski collision trial in recent history.

There are about a hundred code-related lawsuits playing out now outside the spotlight. Most cases are settled before going to trial.

Throughout Paltrow’s trial, the word “uphill” has emerged as synonymous with “guilty,” as attorneys have focused on one of the code’s main tenets: The skier who is downhill or ahead on a slope has the right of way.

Rather than focus solely on the question of who hit who, attorneys have questioned nearly every witness — from Paltrow’s private ski instructors to doctors for the man suing Paltrow — about which skier was downhill at the time of the collision.

After initially suing Paltrow for $3.1 million, retired optometrist Terry Sanderson is now suing for at least $300,000 in damages. Paltrow has countersued for $1 and attorney fees, claiming Sanderson ran into her.

In court, attorneys on both sides have repeated the term “downhill” to try to persuade the jury that their client had the right of way.

The question has become a focal point of the trial, as both sides call legions of family members, friends and doctors to testify in Park City — the posh Rocky Mountain resort town that draws a throng of celebrities each year for the Sundance Film Festival.

Paltrow’s position on the slope was central to the questioning of her teenage children — 16-year-old Moses and 18-year-old Apple Martin.

In depositions read by attorneys in court on Tuesday, the children both testified that they didn’t see the moment of the crash. Before it happened Moses Martin said he saw a man uphill from his mother.”

“I was following my instructor but didn’t know what was going on,” Moses Martin, who was nine at the time, said.

His instructor testified that he didn’t witness the moment of the crash either but approached Paltrow and Sanderson afterward.

Apple Martin, then 11, remembered that her mother was in a “state of shock” after the collision and that she used an expletive to say that a man hit her on the run.

To support Paltrow’s version of events, specifically that she was downhill when the crash happened, her defense team commissioned artists to render advanced animations.

Because no video footage was included as evidence, the recollections of a ski buddy of Sanderson’s who claims to be the sole eyewitness has become a sticking point for Paltrow’s team. In addition to sharing animations, Paltrow’s team undercut the man’s testimony by calling on experts arguing that Paltrow was downhill.

Over objections from Sanderson’s attorneys, the court has allowed Paltrow’s team to play three of the seven high-resolution animations on a projector positioned between witnesses and the jury box — showing the pruning on Deer Valley’s aspen trees, children’s ski coats and groomed snow on the beginner run where Sanderson and Paltrow crashed.

Irving Scher, a biomechanical engineer hired by Paltrow’s defense team, drew stick figures and line graphs on a whiteboard, as well as jotted down equations calculating force and torque to argue that science supported Paltrow’s account.

“Ms. Paltrow’s version of events is consistent with the laws of physics,” Scher testified Tuesday.

In an equally theatrical display last week, Sanderson’s lawyers tried but failed to rope Paltrow into a reenactment of events, when the judge put the kibosh on it.

While there are minor differences in state laws when it comes down to finding fault, “in court it becomes a question of who was the uphill skier,” said Denver attorney Jim Chalat, who has litigated cases in Utah and Colorado.

“It’s the uphill skier who is almost always in a position to cause the crash,” Chalat said. “If you’re skiing too fast for your own ability and you can’t carve out a turn, and you hit someone, you’re going to be in trouble.”

Still, crashes between skiers are rare. Most incidents resulting in injuries or death occur when skiers or snowboarders slam into stationary objects, usually trees. Collisions involving people represent only about 5% of skier injuries, Chalat said.

Experts at the Paltrow trial have argued that the National Ski Areas Association’s more than 60-year-old code is ubiquitous, with similar etiquette in Canada, Australia and parts of Europe.

The responsibility code was recently updated to urge skiers involved in a collision to share contact information with each other and a ski area employee. Last week, Paltrow was grilled by Sanderson’s attorneys for leaving the collision without first exchanging information with Sanderson. She said she knew one of the family’s ski instructors handled that for her.

Very few cases target the ski resorts where crashes occurred because of the inherent dangers that come with skiing and snowboarding, Los Angeles attorney John Morgan of the firm Morgan & Morgan said.

The mountain where the Paltrow-Sanderson collision happened, Deer Valley, was removed from the lawsuit in part because skiers absolve resorts of responsibility by agreeing to a set of rules on the back of every lift ticket.

“It’s like going to a baseball game and you get hit in the head by a foul ball. You know by sitting there that there’s some risk of that happening,” he said.