Two daughters of a retired optometrist suing Gwyneth Paltrow are expected to testify about the lasting effects of their father and Paltrow’s 2016 ski collision as the trial takes on an increasingly personal note.

Lawyers are expected to call Polly Grasham and Shae Herath to the stand and question them about the broken ribs and lasting brain damage their father Terry Sanderson claims he sustained after he and Paltrow crashed at one of North America’s most upscale ski resorts seven years ago.

Neurologist Richard Boehme and Paltrow herself could also be called to testify on either Thursday or Friday.

Dr Sanderson is suing Paltrow for $300,000, claiming she recklessly crashed into him while the two were skiing on a beginner run at Deer Valley Resort in Park City, Utah.

In a counterclaim, Paltrow is seeking $US1 million ($1.5 million) and lawyer fees.

Injuries likely caused by collision from behind

The amount of money at stake for both sides pales in comparison to the typical legal costs of a multi-year lawsuit and expert witness-heavy trial.

During the first two days of trial, Dr Sanderson’s lawyers and expert medical witnesses described how injuries were likely caused by someone crashing into him from behind.

They attributed noticeable changes in Dr Sanderson’s mental acuity to that day’s injuries.

Paltrow’s lawyers have worked to paint Dr Sanderson as a 76-year-old whose decline followed a normal course of ageing rather than resulted from crashing into their celebrity client.

They have not yet called witnesses of their own to testify but in opening statements previewed for jurors that they plan to call Paltrow’s husband Brad Falchuk and her two children, Moses and Apple.

They have thus far attempted to poke holes in testimony from Dr Sanderson’s team of experts and are expected to question his two daughters about their father mentioning Paltrow’s fame and an email alluding to footage recorded on a GoPro camera that hasn’t been found or included in evidence.

Her team has previously accused Dr Sanderson of suing to exploit Paltrow’s wealth and celebrity.

Paltrow is the Oscar-winning star of Shakespeare in Love and founder-CEO of the beauty and wellness company Goop.

-AP