How violent an action truly is is irrelevant when deciding whether a murder was premeditated(first degree) or not(second degree). If I swing a hammer at a wall and someone happens to be passing by, I hit them in the face and kill them, it's going to look very gruesome in slow motion. That doesn't mean I intended to kill the person. If a jury is more likely to think I had time to notice the person passing by because of slow motion and thus believe that I intended to kill the person, then that's an error.

It doesn't even have to be a killing.

The slow motion makes it look like actions were deliberate instead of spontaneous. So it makes it look like a planned action. If the defendant deliberately did it, they must be pretty terrible, right? Guilty of a worse crime.

How often does spontaneous violence occur? If it looks like actions were deliberate and planned, wouldn't you need some other reasoning to believe that they weren't?

Right, but the dangerous part is that slow motion biases our judgement so that we ultimately determine an action was deliberate and planned.

  the slow motion would actually help the jury come
  to the correct conclusion.

For the wrong reason.

The whole point of the article is that it helps them come to the wrong conclusion in a number of cases and your argument is that they must be wrong, because they came to the 'correct', in your opinion, solution in this specific case. That kind of reasoning is awful and immoral.

> come to the wrong conclusion

How do you know which verdict is wrong or right in order to say that though? You can say that slow motion makes people convict more, or convict less, or whatever, but unless you have an oracle to tell you which was the correct verdict in each case, and we don't, this data tells us nothing.

Maybe people are systematically underestimating violence when they don't get to see it in slow motion, and the acquittals when they don't have slow motion are the wrong conclusion.

Or maybe people are systematically overestimating violence when they do have the slow motion and the convictions are the wrong conclusion.

Who knows? But it doesn't really give us anything to go on does it?

  How do you know which verdict is wrong or right in order 
  to say that though?

For the same reason that other things that have unconscious influences are expressly forbidden. A verdict should be based on the facts of the case, not on emotions incited in the jurors. That's why we forbid irrelevant anecdotes that demonstrate what a bad person an accused is. It would lead to the wrong verdict.

After it's been pointed out, the point of the article is entirely obvious: if we see someone take a minute before committing murder, then we will think them of having had sufficient time to think. If it takes 5 seconds, he obviously didn't have time to consider. So if we stretch 5 seconds into a minute, a jury will conclude there was rational deliberation where there was only instinctive response.

What is entirely non-obvious is supposing that brain of the average juror could 'just' compensate for his impressions based on the knowledge that it was shown in slow motion. We know they aren't capable of that with many, many other cognitive weaknesses. Sources: Influence, Thinking Fast and Slow, Predictably Irrational, ...

Good point.

But in sports, slow motion is often enlightening. After a tackle, we see a soccer player collapse to the ground, writhing in agony, clutching their shin. But then slow mo shows that the other player never even made contact with them, its a classic "dive". In that case, there's no doubt that the slow mo version is more informative.

You need a replay for that, but you rarely need slow motion for that.

" I think the average person underestimates the violence inflicted by a bullet because our human intuition fails us for small objects traveling that fast"

My opinion is that this is caused more by glamorization/trivialization of violence (in all its forms) by the US movie industry.

I tend to agree with this. One of the things which struck me about gang violence in LA is that if you have even one gunshot wound you really are out of action. Contrast that with pretty much every depiction on screen or television where people continue fighting.

There's two equal and opposite misrepresentations of reality. If you're not either the main bad/good guy then a single gun shot or punch will take you out completely. Often people fly backwards from a gun shot, which is just crazy. Conversely, if you are the main hero/villain, you can probably get shot 10 times and be beaten with a lead pipe across the head quite a few times and still be going along just fine.

Nailed it.