Final answer:
An amateur bank robbery might be indicated by poor planning, lack of sophistication, ineffective disguises, leaving behind evidence, and not understanding that most money is now digital. Witness descriptions with high uncertainty further support the idea of an amateur robbery.
Step-by-step explanation:
A good indication that a bank robbery was committed by an amateur may include a lack of sophistication in the method of the robbery, leaving behind evidence, or the absence of a clear escape plan. Based on the scenario provided, where the suspects lack direct evidence linking them to the crime but have been found to carry unlawful weapons, it might be that their overall preparation and execution of the heist were poorly planned, leading to early suspicion and apprehension by the police.
When police officers identify criminals, they rely on evidence and witness statements. Descriptions like "medium height" or estimates like "between 5 foot 8 inches and 5 foot 10 inches" indicate a significant amount of uncertainty and could suggest that the suspects did not disguise themselves effectively, which is another sign of an inexperienced criminal. Additionally, the fact that most money today is in the form of bank accounts as electronic records makes it more challenging for robbers to access, suggesting mistakes made during the robbery could indicate a lack of understanding of modern banking practices, a hallmark of an amateur.