Nevertheless, I will defer to a real expert. I suffer no illusions that "expert witnesses" are not paid well to say whatever their client needs them to say, but unlike psychology or economics, Physics is a pretty damn exact science. Rarely, if ever, do objects defy the laws of Physics.
In his original report, submitted back during the Grand Jury days, Hayes wrote this:
From a careful review of the autopsy report and post-mortem photographs, we determined that Lauren’s massive, traumatic injuries were consistent with a single, high velocity impact to the cliff face. Her injuries could not be explained from her sliding and tumbling down the cliff face or with multiple impacts to the cliff face before landing in the water of the inlet. ...
Basically, Hayes believes (and this trial is his third appearance) that Lauren could not have slipped and fallen and rolled without suffering certain types of injuries. The defense witness of the first trial (not sure who Harris has this time) said that the side of the hill was composed of soft, dry grass and not rocks. I don't know how convincing he was, but apparently not very - since none of the jurors voted to acquit.
Denise Nix reports in The Breeze:
Hayes and an associate also conducted trajectory experiments to see how fast a reasonably healthy adult man could throw objects in the 40- to 45-pound range, like Lauren.
Based on Lauren's injuries, the path the weights took over the cliff and the topography of the rock face, Hayes concluded that she was launched head first, hit her face and upper body on an outcropping before bouncing into the ocean 120 feet or so below.
At the last trial, Hayes showed a PowerPoint presentation including huge autopsy pictures, close ups of Lauren's injuries in her face, wrist, and chest. These pictures, combined with the upcoming field trip to Inspiration Point, are likely the most damaging evidence and will haunt the jurors for years.
Hayes probably showed the same topographical maps and land surveys and once again described that fundamental Physics will demonstrate how this object moved in space, what type of trajectory it had to have in order to land a certain way inflicting certain injuries. If the object had slipped and skidded down, it would have moved at a rate of 4.6ft/second. If thrown, the object falls at 15ft./second. It's very convincing, and it's hard to refute the laws of Physics.
The same team that brought us "The Incredible Running Leap Theory" is trying to claim that Brown would have fallen along with the child if he threw a 43-pound weight off the end of the cliff. A fit, athletic man who literally threw 43-pound objects hundreds of times daily for a living at the time, lacked the balance and skill to heft a 43-pound child 12 feet or so into the air over an edge? Really?
Sure, Hayes was paid, he was good, he has a good reputation. He's no different than any number of paid experts that testify at trials every day. That the Kaldis Twins want to impeach him is perfectly normal. However, unless the defense can better demonstrate how an object can move down a cliffside and has the video to prove it, they will be hard-pressed to outshine Hayes.