https://www.theguardian.com/us-news/2024/feb/20/donald-trump-trial-calendar-schedule-dates
An example of why investigations of the country’s most powerful people need to be protected from those same people. A good reason to have a separate fourth investigative branch of government.
Of course, even then there is a potential for corruption of the head of the investigative branch is being investigated, but there can be a special procedure for that in the investigative branch itself, such as assigning a special investigator.