When is expert opinion inadmissible?

The expert — the person with the special knowledge (the science, art, trade-or-experience) beyond the ordinary person's — whose opinion the court may receive on the relevant matters (the Evidence Act's expert-opinion provisions — the opinion-evidence's exception: the general rule's exclusion of opinions vs the expert's admission). The nature of the expert's opinion: the opinion's-not-fact's character (the court's weighing); the corroboration's rule (the expert alone rarely convicts — the court's own judgment retained); the expert's duty (the court's assistant — the objectivity's ethic; the partisan-expert's criticism). The forensic experts' catalogue: the medical (the post-mortem's doctor), the scientists (the DNA, toxicology, ballistics, documents), the fingerprint examiners, the digital forensics — the labs' and the hospitals' experts.