who gives expert view on the facts in their area of their expertise
Expert witness An expert witness, in England, Wales and the United States, is a person whose opinion by virtue of education, training, certification, skills or experience, is accepted by the judge as an expert. The judge may consider the witness's specialized (scientific, technical or other) opinion about evidence or about facts before the court within the expert's area of expertise, referred to as an "expert opinion".[1] Expert witnesses may also deliver "expert evidence" within the area of their expertise.[2] Their testimony may be rebutted by testimony from other experts or by other evidence or facts.
Mathematician To develop accurate models for describing the real world, many applied mathematicians draw on tools and techniques that are often considered to be "pure" mathematics. On the other hand, many pure mathematicians draw on natural and social phenomena as inspiration for their abstract research.