Plea bargaining is one of the most important aspects of criminal defense practice. Like most vital areas of real world law, it is not taught in law school. All PB experience happens on the job.
One of the aspects of the plea bargain is talking with your ADA about problems with the case. For example, you may point out that the arresting officer isn’t very strong on the stand, or has recently been arrested etc.
Such statements are usually made with a request for a specific disposition; a dismissal or better plea terms. Most ADA’s have more than enough cases set for trial, many don’t want to waste time presenting a problem case to a jury.