this is approx. 1.5 minutes of a columbo episode where he careens down a hill. i think it is a genuine fall, and he "ad libbed" what he said relating to it, and the director decided to use it. most people who comment on this video also think the fall is real.
i looked at the clip carefully a number of times, and i can completely see the progressive loss of control that falk experiences as he walks down the slope and then he starts trotting down the slope unexpectedly due to his insufficient expectations of how much he should apply his muscularity to resisting the descent's pull.
when he gets to the point of no return, he is then compelled to use a wider and wider gait until he lands in the ditch.
he still had his cigar in his fingers when he landed which seemed suspicious to me, and also it seemed to me on the first viewing that there seemed to be a convenient bed of straw for him to fall into.
on successive watchings, i realized that what i saw as a straw cushion was just a thin covering of dead grass, and i studied the thickness of the dead grass at the bottom of the ditch , and i decide it is not sufficient to break a fall, and i conclude the sequence was a real life "blooper" (as they call it), and it was left in the shoot because it worked very well because falk ad libbed in the way columbo would be expected to respond to such a situation.
here is the clip.
[youtube]http://www.youtube.com/watch?v=-HT1plNt1L8[/youtube]