An entry at The Panda's Thumb rebuts Michael Behe's proposed falsifiability test for ID. During the Dover trial, he testified that
In fact, intelligent design is open to direct experimental rebuttal. Here is a thought experiment that makes the point clear. In Darwin’s Black Box, I claimed that the bacterial flagellum was irreducibly complex and so required deliberate intelligent design. The flip side of this claim is that the flagellum can’t be produced by natural selection acting on random mutation, or any other unintelligent process.
To falsify such a claim, a scientist could go into the laboratory, place a bacterial species lacking a flagellum under some selective pressure, for mobility, say, grow it for 10,000 generations, and see if a flagellum, or any equally complex system, was produced. If that happened, my claims would be neatly disproven.
This, of course, is untrue. Since the purported designer is unknown not necessarily knowable neither of the two outcomes "prove" anything.
- If the bacteria develop flagella then by their own claims it proves that it must have been designed
- If the bacteria to not develop flagella then we can assume that the designer chose not to create them
The important point to remember when talking about Intelligent Design as a science is that the Designer acts at their own whim and can not be forced into acting, either through experiment or in the world at large.