> there is a 50% chance that in general all the evidence has a 50% chance of being fake

No, not all evidence - only the one needed for the Parallel Construction.

Just because there are 2 possibilities doesn’t mean they’re both equally probable.

"it's equally possible"

The word equally possible implies equal chances for me. Otherwise it is equally possible, that the evidence was in fact planted by aliens.

For what it's worth, to me, "it's equally possible" means "it's also possible, however remotely". I know it doesn't make sense, but, then again, neither does "I could care less".

I think in casual speech "equally possible" usually is taken to mean "also possible." I think most people would say "equally likely" to express what you're saying.

Thank you, I am not a native english speaker.

For what it’s worth, I am a native English speaker and I disagree with the other poster. I would interpret “equally possible” similarly to how you did.

Thank you, I suspected as much. That it is at least ambiguous.

Isn’t English fun?

I think “possible” has a less precise connotation than “probable” which suggests some statistics.

Imagine believing that cops don't plant evidence. LOL

You don't have to believe it never happens to believe the odds aren't 50%. It provably does happen, but 50% is a high probability.