What constitutes possession of a drug in ohio?

[Sharr21]

My fiance went to court for arraignment for a dui today and was arrested in court for possession of lsd. When he was arrested over the weekend, he was placed in a police car for transport to a holding cell in the jail. Their basis for arrest was that when they cleaned the car out 4 days after his arrest, they found lsd in the car that he was transported in. Only he knows for sure if he's guilty or not, but I thought possession meant that you actually had to have possessed it and been found possessing it. Since it was nowhere in his possion, was not holding it anywhere on his body, or in any area of his car, or bags that were his, how can they say that he possessed it? The dictionary defines "possess" as to have and HOLD as property. But I need more help with this one.

Thanks,
Sharron