Here's a list of things in my opinion that should and shouldn't be used as evidence. This list is mainly for 2 imposter game:
"Red sus" – not evidence unless another piece of evidence is provided.
"I saw Blue go into Electrical and then I went in and they weren't there" – evidence – if the claim is correct, Blue probably vented.
"Green took like 20 seconds on the download task" – evidence – if the claim is correct, there is a 90% chance that Green was faking it.
"Purple faked accept diverted power in Reactor" – evidence – the Accept Diverted Power task in Reactor is a fake task – you can't divert power to Reactor.
"Lime faked card swipe/boarding pass/wiring/keys" – evidence (if the task claimed to be faked is a task you don't have) – with common tasks, either everyone has them or nobody has them.
"The taskbar didn't go up when Black did a task" – evidence (if Taskbar Updates are set to "always") – Unless it is a multi-part task. If they did the admin upload but the bar didn't go up, get 'em out. If they did the wiring without the bar going up, that ain't proof unless you don't have the task, in which case the above statement applies about common tasks. If they did Accept Diverted Power and the bar didn't go up, get 'em out. None of this except the common tasks one applies if Taskbar Updates aren't set to "always".
"it white he follow me" – not evidence – players rather commonly follow other players for multiple reasons; White could've been checking your alibi, making sure you weren't killing, keeping both himself and you safe, getting themself an alibi, and way more than that.
"Cyan just killed Brown in front of me!" – evidence – if you think this isn't proof enough for you without a counter-accusation, something is wrong.
"Blue vented in Electrical" – evidence – see above reason.
"I saw Purple go into Medbay and then I went in afterwards and Red was dead on the scanner" – evidence – if the statement is true, Purple killed Red and vented away.
"it pink she kil my sister/brother/friend/fellow moron" – while this is technically evidence, I say you should throw out everyone who does this and then either pretend you didn't see it, let the Imposter win, or turn it into Hide and Seek.
"Green faked Prime Shields/Submit Scan/Clear Asteroids/Empty Garbage" – this one depends – if you are on MIRA HQ, the only visual task is Submit Scan. If they fake that, they probably stabbed White. If you're on Polus, Clear Asteroids and Submit Scan are the visual tasks. If they fake either of those, they probably just shot Red. If you're on The Skeld and they faked any of these, my theory's that Green had murdered Brown. Of course, if Visual Tasks are off, none of this matters and it isn't evidence.
"I think I saw Lime teleport, is that venting or…?" – not evidence – one of the two players in this interactions is lagging and probably has a high ping.
"White took too long on Card Swipe/Start Reactor/Fix Weather Node/[insert any other task that can take multiple tries here]" – not evidence – some people are just flummery at tasks.
"I was with Green and Blue the whole time, White, Yellow and Black all saw eachother do visual tasks, Orange did Weapons in front of me, Blue and Green and Brown is dead, which has lead me to my deduction that Purple and Red are the Imposters" – evidence – this is a smart man's game and the player who said this has used the process of elimination. Let's say this player is Lime. I'm going to make a list and cross our suspects off as we go. Lime, Green, Blue, White, Yellow, Black, Orange, Brown, Purple, Red. That is our 10 player lobby and suspect list. The first thing we can tick off is that neither Green, Lime or Blue did it – they were together the whole time.
Lime, Green, Blue, White, Yellow, Black, Orange, Brown, Purple, Red. if White, Yellow and Black all saw eachother's visual tasks and nobody denies it, that ticks them off as well. Lime, Green, Blue, White, Yellow, Black, Orange, Brown, Purple, Red. Orange did Weapons in front of 3 other people, which narrows it down to Lime, Green, Blue, White, Yellow, Black, Orange, Brown, Purple, Red and Brown is dead. That leaves only Purple and Red as our potential imposters, meaning that one of the committed the crime and the other is the partner in crime.