How can you have 4 outs in one half inning?

You can't - only three outs. BUT you can have FOUR strikeouts in one inning. If the catcher drops the ball, the runner can go to first base, but no out is scored.

0-0 1 Out, runners on 2nd and 3rd

Fly ball

The runners both run home (2-0)

The ball is caught (2nd out)

The defender tags 2nd base (3rd out, score is now 1-0)

  • At this point, the inning is over. The defense may run off the field and the score will remain 1-0, OR they can tag 3rd base to record the 4th out and the score will be 0-0

Actually, from what you're saying, neither runner that scored tagged up. So when the outfielder caught the ball for the 2nd out, then threw it to second for the third out, the inning was over. The run does not count because the other runner never tagged up.

in other words, the first poster was right. It is impossible to have four OUTS in an inning.

the answer above is correct. the fourth out will only come into play if the defensive team appeals the runner from third not tagging up. if they don't then the run does count. if they do appeal the play the runner is out (the fourth out) and the run does not count

the answer above is correct. the fourth out will only come into play if the defensive team appeals the runner from third not tagging up. if they don't then the run does count. if they do appeal the play the runner is out (the fourth out) and the run does not count