This deals with Radar, Missing people, Known people who are living, and KOSing whoever is left. This works only if a disguiser does remove your blip from the radar. So, Let's say 9 people are 'alive'. 1 known to be dead, body cannot be reached. The other 8 need to be confirmed. 3 are Ds, all alive. I've seen the other 4. So, if the disguiser does remove you from the radar and you know who it is you cannot find would it be correct to KOS this other person who is not appearing on the radar? This is basically a situation I've ran into today, it makes sense to me if the disguiser functions like so and that info is known.
If you have absolute certainty there are no other blips on your radar, and the disguiser does indeed hide players on the radar then yes. But this is so prone to error that I wouldn't even attempt doing.
https://www.seriousgmod.com/threads/can-you-kill-off-of-a-radar.20015/ We had a pretty long debate in Staff Discussion about this back in May, and it was decided that using the Radar as grounds to KoS / kill someone in these situations is perfectly valid.