Amy Joyce has found this article about the airing of the films in the courtroom during the Ruby trial. It includes the comment from Ruby that he didn't remember the garage as being so crowded. Of course, it wasn't when he was there. A policeman with a yardstick pointed to and identified Ruby, but of course, it wasn't true.
How could Ruby's lawyers not see that the Garage Shooter was not their client? Did they make any effort to compare him? Mentally, did they ever enter the mental space of questioning whether the Garage Shooter was really him? No, they did not. And I suppose it came down to "belief in America" the belief that American police would never lie about a thing like that. But, this was a huge failing on their part. And especially after Ruby told them that he didn't remember it being so crowded in the garage. I suspect it was just a small number of people when Ruby was pounced upon and dragged off. And that had to happen at an undetermined time before.