Unless that person explicitly tells you they want to come out, but are too scared to say something themselves and need you to do it, don't. Just don't. It not the type of thing you just blurt out.
Don't. It sucks being cornered into admitting it. I personally know people who I could very well out because they have been malicious towards me, but I choose to ignore them.. at the end of the day you need to focus on yourself and not the lives of others.
Like I'm basically out, but I don't explicitly tell people for the sake of telling people. So if they find out from others, I'm actually kinda thankful for it, because then there's no more awkwardness of wondering whether they know or not, etc.