Final answer:
In a trial, a jury typically determines whether Juliette has stolen the purse, though a judge may decide in a bench trial if the right to a jury is waived, all while upholding the presumption of innocence.
Step-by-step explanation:
If Juliette is tried for theft, the question of whether she has stolen the purse will generally be decided by a jury in a criminal trial. This reflects the presumption of innocence, a foundational principle of criminal law that assumes any accused individual is innocent until proven guilty beyond a reasonable doubt. In some cases, if the defendant chooses to waive their right to a jury trial, a judge may decide the case in a bench trial. However, the standard of proof remains the same. The jury (or judge in a bench trial) must evaluate all the evidence presented, including the video footage and Juliette's claim that she is not the person in the video, to determine if there is sufficient evidence to establish her guilt.