Dutch criminal law does not provide a legal definition for the term "expert" nor the "expert witness." Common practice indicates that Dutch courts will only admit experts' opinions when they are satisfied with the expert's skills, training, and experience, although the way in which this is judged is unknown to the public and the defense; however, this practice also makes it possible for the defense attorney to persuade the court to regard the layperson of today as the expert of tomorrow. This report focuses on two groups of expert witnesses, i.e., forensic experts and behavioral science experts. The decision to admit the expert's report or the expert witness's testimony into evidence as expert opinion is left to the trial judge. Given the uncertainty of the standards, qualifications, and criteria for determining the reliability of experts' qualifications and the soundness of their testimony and opinions, judges, prosecutors and defense attorneys must be alert to flaws, errors, false-positive identifications, and biased opinions. In order to enhance the reliability of expert testimony and increase the likelihood that flawed expert testimony will be exposed, this paper proposes that a legal definition of the term "expert" be included in legislation. It also recommends that a witness only be regarded as an "expert" after proper continuous training and proven skills and when registered in a national database and sworn by the court. The protocols of each research project in forensic and behavioral science must be accessible to other experts and the defense attorney. Also, each suspect and/or defendant must be awarded the legal right to a cost-free expert who can dispute an expert's opinion presented in the prosecution's case. Finally, courts must indicate in their rulings the reasons for admitting an expert's opinion as evidence while not admitting an opposing opinion that claims to have authoritative status.