If I were the judge, I would overrule the objection and admit the evidence. The evidence has some (albeit small) tendency to prove lack of seatbelt use.

Here's another hypothetical:

In a drug conspiracy case, the prosecution charged Smith, Jones, and Harper with conspiracy. The evidence showed that Smith and Jones went to Mexico, bought a large supply of Ecstasy, fly it into Indiana by private plane, and then started selling it to I.U. students. When arrested, Smith and Jones both convinced the U.S. Attorney to give them favorable plea bargains in exchange for their testimony naming Harper as the drug kingpin who set up and financed the whole operation. Harper is a professor of history at I.U. who is baffled at the accusation, says he has never heard of Smith and Jones or had anything to do with drugs, and whose defense is that Smith and Jones must have picked his name at random from the phone book. The prosecution presents a DEA agent who testifies that when he searched the apartment in which Smith and Jones lived, he found a piece of paper with Harper's name and phone number written on it. The prosecutor offers the note into evidence.

What objection could the defense make?

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