Ski instructor Eric Christiansen is now being cross-examined by Gwyneth Paltrow's lawyer after giving evidence earlier in the trial
Earlier, Terry Sanderson, 76, who accuses Gwyneth Paltrow of causing a ski collision with him, said he remembered a "blood-curdling scream" just before being hit
He was answering questions from his attorneys about his post-concussion symptoms before being cross-examined
The family of the Hollywood actress are due to give evidence in the case sparked by an accident at an upmarket resort in Utah in 2016
The court expects to hear from Paltrow's daughter Apple, son Moses, husband Brad Falchuk as well as two ski instructors
Sanderson is seeking $300,000 (£245,000) in damages for the incident that took place on a beginners' slope at the Deer Valley resort
Oscar winner Paltrow, 50, denies she was responsible and has countersued - seeking $1 in damages, plus legal fees
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We're back in court and we are hearing from plaintiff Terry Sanderson's eldest daughter.
Shae Herath is clearly quite emotional as she sits in the witness box. She starts by talking about the close relationships she had with her sisters growing up.
Sophie Long
Los Angeles correspondent
Image source, EPA-EFE/REX/ShutterstockWhat’s at stake must be at least partly reputational.
Gwyneth Paltrow is not only famous for being an Oscar-winning actress, and an A-list Hollywood star once married to a British rock star, but more recently for her multi-million dollar wellness brand Goop.
Now the actress is half-way through a trial in which she stands accused of not only recklessly causing a crash that resulted in a 70-year-old man sustaining serious injuries, but also of leaving him lying in the snow without checking he was alright.
Paltrow, of course, vehemently denies both those accusations.
This can’t be about the money, Terry Sanderson is seeking damages of $300,000 and Paltrow has counter sued for just $1 and her legal expenses.
For him this is about holding someone accountable for the decline in his mental health and she is seeking a moral victory to clear her name.
Sophie Long
Los Angeles correspondent
This is day four of what is slated to be an eight-day trial and Gwyneth Paltrow has been in court throughout.
On the first day of the trial her legal team complained about cameras being on her at all times, as she looked distracted by her phone.
They also complained about reporters getting too close to her as she left court. But since then she has looked more relaxed.
To date this has been an expert witness-heavy trial, but there was testimony from one of Sanderson’s daughters yesterday who became emotional as she talked about the changes she had encountered in her father since the accident.
And today things should get more personal still as we should here from both Sanderson and Paltrow herself.
Image source, EPA-EFE/REX/ShutterstockTerry Sanderson
Sanderson's legal team wrap up their questions after Herath admits he can only "take Terry in small doses now" referring to how their friendship has deteriorated since the accident.
Paltrow's lawyer then quizzes Herath about his friendship with Sanderson but don't spend long being on their questions.
There are no further questions from Sanderson's legal team and Herath leaves the stand.
Court is now taking a short break and we will be back in a moment.
More from Herath who says he wasn't with Sanderson on the night he was injured on the slopes, but that he'd had a call.
He says he wasn't surprised that he'd suffered an injury.
Herath continues: "He said that when Paltrow hit him, then that whoever she was skiing with left the scene.
"That is what surprised me."
Sanderson's defence team asks why and Herath recalls a time when he was younger when someone he knew got hit on the slopes in Colorado.
He adds: "it is a serious offence and something you just don't do."
The court audio feed cuts out as the legal teams approach the judge.
Paltrow can be seen shaking her head.
Herath is asked if he ever worried about Sanderson whenever they went skiing together.
"I did not, it was pretty clear to me that he had been quite the athlete when he was younger because he was a very strong skiier," Herath replies.
Asked if - prior to the accident - he ever recalls Sanderson being forgetful, to which Hearth says no.
He's then asked if he remembers Sanderson ever forgetting ski gear. Herath says he has no recollection if that happened.
Herath confirms he was not skiing with Sanderson on the day of the accident. He recalls getting a call from Sanderson on the evening of the incident telling him of the accident.
"He didn't give any details at that point. Just concern about how he was going to get back from Park City," he adds.
He's asked then if Sanderson was confused about how he was going to get back home.
"He had no idea," Herath says.
Former Navy pilot Mark Stephen Herath is testifying in support of the optometrist's case. The pair used to ski regularly together.
He rates Sanderson's skiing as "advanced to intermediate" and says he never witnessed him have any accident in that time
Describing Sanderson before the incident in 2016, he described Sanderson as "very outgoing, loved a good conversation - reall enjoyed being around people. Very active".
"Intelligent, witty, sharp - always interested in what you were doing," he adds.
Herath says he knew the plaintiff Terry Sanderson for 15 years or so.
"He was gracious enough to ask me to let me stay at his house," he says.
"We grew through skiing, we used to ski together.
"Terry knows my son, my daughter and my wife really well. My son calls him uncle Terry."
Herath describes his friend as someone who was sociable before his accident and that he was a strong skier.
Dr Boehne has finished giving evidence and Sanderson's legal team call their next witness - Mark Stephen Herath.
He takes the oath and starts by giving some background on who he is and how he knows the plaintiff.
Paltrow's lawyer states there are various claims in Dr Boehne's deposition about the length of Sanderson's loss of consciousness.
The neurologist agrees there was some variety of opinion about how long Sanderson may have lost consciousness.
He says you don't need to have your eyes closed to lose consciousness: " I am not saying Mr Sanderson was knocked out," he adds.
"He just had a loss of consciousness - that's it," he tells the court.
Dr Boehne continues his testimony as he talks through the calculations and ruling out certain possibilities.
He says he just wanted to know what the magnitude of the force application was when the crash happened.
"One of things I didn't have is the initial speeds at the time of impact," he recalls.
"I don't know how fast they were skiing."
Dr Boehne is now asked about the calculations he made to rule out the possibility Paltrow was hit by Sanderson.
Comments are being read out from Dr Boehne's previous deposition, where he said he ruled that scenario out because he would expect Sanderson's rib fracture to be in a different place if that were the case.
He says he did not have the skiers' initial speed on the time of impact when making his calculations.
The court is then shown equations he made to come to the conclusions he provided in court.
We're currently listening to Dr Boehne who is appearing for the plantiff Sanderson being cross-examined.
Dr Boehne says he believes his account of the accident - that Paltrow hit Sanderson from behind - is the only possible account "given the set of facts that were given to me and the nature of the injuries sustained" by the optometrist.
Sanderson was hit in the back from the left; some of his ribs fractured on his elbow as he hit the ground, Dr Boehne maintains. Those injuries could not have been sustained by Mr Sanderson hitting Paltrow from behind, he states.
Dr Boehne calculated the nature of the accident according to "classic physics" he says, but concedes that he "guestimated" Gwyneth Paltrow's weight at 130 pounds.
The court has returned from recess.
We'll now hear more from Dr Boehne.
The court is now taking a short recess.
Stay with us and we'll bring you the main developments as soon as it returns.
Dr Boehne is continuing to give his testimony as he is cross-examined by Sanderson's legal team.
He has been talking through his handwritten notes he took down back in 2016.
As the neurologist is giving his evidence via videolink, his notes are being shared on the same screen as the legal team scroll through the paperwork.
Neurologist Boehne is now being asked about his expert evidence about Sanderson's injuries.
Boehne is saying that his job, from a biomechanics perspective, is to determine how Sanderson's injuries may have come about.
He is asked whether he has an opinion on whether anyone was skiing unreasonably when the collision happened.
"I have no comment on how anyone was skiing," he says.
Neurologist Richard Boehne is currently giving evidence before the court by videolink.
He is being questioned about previous testimony by medical experts on behalf of Terry Sanderson.
Dr Boehne is being asked if he agrees with Sanderson's witness characterisation of the accident.
The witness has cast doubt on the suggestion that the retired doctor's deterioration came directly after the collision, as well as saying there is evidence Sanderson only suffered a mild concussion.
Day four of the case is now under way in the court in Park City, Utah.
Terry Sanderson and Gwyneth Paltrow's lawyers have been addressing the judge about a procedural matter.
Now Paltrow and Sanderson have entered the court and the jury has been brought in, testimony has begun for the day.
Stick with us for key revelations and analysis of the case.
The spotlight in this trial hasn't just been on the Hollywood actress.
So far, the lawyers in the case have been at the centre of attention.