When investigating Brenton Butler, the investigators should have done the following two things:
1. Conduct a thorough and unbiased investigation: The investigators should have gathered all available evidence, interviewed witnesses, and examined any physical evidence related to the case. It is crucial for investigators to approach the investigation with an open mind and avoid any preconceived notions or biases that could potentially lead to wrongful accusations or conclusions.
2. Verify the alibi: In Brenton Butler's case, it was later revealed that he had a solid alibi, which could have been verified during the investigation. The investigators should have thoroughly checked Brenton's alibi by interviewing witnesses, examining any supporting evidence, and ensuring that his whereabouts during the time of the crime were accounted for. This step is essential to either confirm or eliminate him as a suspect and prevent wrongful arrests or charges.