Juror #4 points out the boy's alibi. Where was the boy supposedly when the murder took place, and why does #4 find the alibi flimsy?

Juror # 4 states that the boy's entire alibi was 'flimsy." The boy claimed he was at the movies at the time of the murder yet an hour later he could not recall the title of the movie or the actors in it. There were also no eye witnesses who could place the boy at the theatre.