What sort of official Certifications are needed if I’m not a doctor?
Every field holds its most skilled professionals to a standard. Training, licensing, and experience all contribute to meeting that standard.
Many fields require a license to legally do their job. Professional Boards exist in every State to protect consumers by guaranteeing a certain quality of experience and training.
College or trade schools offer degrees and/or credentials on completion of a course of study. In forensic work, that degree and/or credential further qualifies you to testify. The more rigorous the standard, the more respected the school, the more oversight from a licensing Board, the easier it will be for an expert to defend the reliability of their opinions on the stand.
Attorneys are ethically bound to provide their clients with the best possible representation. Therefore, if an expert witness is needed, they consider quality in an expert first.