There aren't any slips to heat. You can rig anything on television but there's a live audience that includes people who the rigging would hurt. The drawing is done by drawing four numbered balls from among 14. There are 1001 such combinations of 4 numbers. Each of the 14 teams is assigned the number of combinations that is appropriate for their stated odds. One combination is not used and if it shows up they redraw. IIRC, the balls are tested for uniformity in size and weight so eliminating crude mechanical fixes. The companies that supply the equipment do lots of lottery type drawings so they're going to be careful of their reputation. At least so one imagines.
Now, once Monk detected a rigged lottery - I think they used radioactive paint on some of the balls so those wouldn't be selected or maybe so they would be - it triggered an air jet that blew the ball away from the selection opening. Something along that line...