What amazes me is they ran checks on the Caprice so many times without realizing they were finding it near almost every shooting. That would have been the first thing I would have looked for: finding repeating patterns in data is standard problem-solving methodology.
Many people posted that the "white van" was a self-fulfilling prophecy: they are ubiquitous on the road, and the probability of seeing one at any given moment is near 100%. The task force should have figured this out, too.
But, what really astonishes me was their inability to recognize the significance of the unusual phrases used in the note(s). Google would have told them the relevance in a matter of seconds.
Yeppers. A simple SQL query would have sorted that puppy right to the top of the list.