strategy when opponent is in time trouble

Hi, I was hoping I could tap the brains of some of the good blitz/rapid players here on a question that has come up in a few OTB games my son has played in recently.  Specifically, when your opponent runs into time trouble, but you have an adequate amount of time left, and you are losing in the game, does it make sense to rush your moves so that your opponent won't have enough time to think during your time?

My son did this recently in a G/45, and it worked, as his opponent ended up flagging.  He also did it in a blitz game, where his opponent had like 20 seconds left and my son had like 1 minute 15 seconds left, and it did not work, as my son played very poorly in those moves, and went from being down by a few pawns to getting checkmated (with the opponent having 5 seconds left on her clock).

What do people think/recommend?

The problem with playing rapidly in your opponent's time trouble is that your advantage on the clock no longer matters, unless your opponent is in immanent danger of flagging. If you are going to blitz out your moves, then it might as well be you (instead of your opponent) who is short of time.

In effect, blitzing during your opponent's time pressure is a way of "leveling the playing field"... so it is worth doing only under one of two circumstances:

1) if you are already losing anyway, then leveling the playing field is a good tactic.

2) if your opponent is so short of time that he is in danger of flagging, then keeping the pressure on might be a good tactic.

Here's the thing, they may be in time trouble *because* they're better under the pressure.  In my opinion, the best thing to do if you have a significant time advantage like that is to muddy up the position.  Instead of making obvious recaptures, go ahead and look for those in-between moves and speculative sacrifices - don't necessarily make them if they're bad, but definitely look for them.  Look for tricky tactics - even if they don't lead anywhere, al long as you make them have to think about it, too.

Your son is obviously smarter than you are.  When your opponent is in time trouble, you run his clock out.   

If you make fast moves, then you are effectively in time trouble.  The best thing is to try to complicate things if you can.

As an aside.  I once knew a strong player who was always in time trouble.  Most of his opponents would make fast  moves to prevent him from "thinking on their time."  Their problem was that he was a top 5-minute player, and they were effectively playing his game.  He won most of the games.