In law, there are two kinds of witnesses: expert witnesses and “fact” witnesses. A fact witness is someone who personally, with his own senses, “saw” the accident with his own eyes, or “heard” the violent threatening language or “smelled” the poison before it was administered to the victim, who tasted the quality of a sample of the vintage wine before it was stolen, or touched the gun left at the crime scene and felt it still hot.
An “expert” witness is someone whose education and specialization permits him or her to draw inferences and/or render opinions which will “help” the Judge and/or Jury to decide the case: how much would the real estate have been worth in the absence of the fraudulent misrepresentations? Is the painting a genuine “Matisse” or “Renoir” or is it a fake? How long would the victim have lived but for the airline crash and how much income would he or she have produced for her family and/or corporation? What was a fair market value for the stock absent insider trading the day before a public disclosure leads to bankruptcy?
In law, the words “proof” and “persuasion” can be used almost synonymously.
The beginning of a civil lawsuit is called, appropriately enough, a “pleading”. In a Plaintiff’s COMPLAINT or “Initial Petition”, an injured party PLEADS for permission to present and prove his case to a jury. The Complaint will be judged by the “legal sufficiency” of the “alleged” (but not proven) facts said to constitute an injury or “cause of action” for injunction or declaratory judgment. For a Past Injury, the remedy usually sought is monetary damages. For future injury, where no injury has happened at all yet, the remedy usually sought is an INJUNCTION to prevent the injury. For doubtful or unclear, debatable injury, a plaintiff might seek a “Declaratory Judgment” that such and such conduct or events DID or WILL constitute an injury, so that the plaintiff can THEN sue for damages or an injunction. Civil Rights suits often take the nature of “declaratory judgment” actions that a law or policy should be DECLARED inconsistent with the constitution.
The Plaintiff, the person bringing the complaint, first has the “Burden of Pleading” (i.e. STATING AND OUTLINING THE FACTS IN A PLAUSIBLE STORY). Once a judge finds that a plaintiff has sufficiently PLED a Plausible story which might entitle that Plaintiff to some sort of relief, Legal Damages = Money, Equitable Damages = An order of Injunction, stopping or commanding certain actions be taken, or Declaratory Judgment, the Judge then requires the Plaintiff to present evidence sufficient to PROVE his allegations of fact.
PROOF means PERSUASION in law. A fact in law is usually a verbal statement. Physical or Visual evidence can come into court, but it must be brought by a person who can describe and analyse the physical evidence and explain it to the judge or jury. The murder weapon never walks into court alone: someone has to bring it, and the person bringing it must tell a story which plausibly connects the gun to someone’s death; there must be narrative, a commentary, a report.
Legal proof would clearly frustrate Eliza Doolittle from Shaw’s Pygmalion or “My Fair Lady” in which Eliza sings:
“Words words words I’m so sick of words; I get words all day through first from him now can you, is that all you blighters can do? Don’t talk of stars, burning above, if you’re in love: SHOW ME! Tell me no dreams, filled with desire, if you’re on fire: SHOW ME!”
Demonstrative evidence has almost no place in law or legal proof at all, although a few instances can be imagined, but even the demonstration must be described, usually by experts, in words.
The “proof” in law is not formulaic. There are quite simply no “a-square + b-square = c-square” formulas in law. And if mathematical formulas are used, they have to come into court by way of expert testimony. You’d better have Pythagorus on retainer if you want to introduce his theorem for any reason……or maybe one of his students or followers.
Ultimately, in law, “proof” is achieved by getting the Judge or the Jury to agree with one or the other of a minimum of two competing arguments or explanations regarding the existence or meaning of any fact.
In a typical civil case, a judge or jury must merely conclude that it is “more likely than not” that any given fact or inference from a fact or series of facts is true. This is called “proof by a preponderance of the evidence” and is sometimes said to equate with 51% probability. A VERY narrow margin of proof indeed. In certain civil cases, family law and probate law especially, “clear and convincing” evidence is said to be required, although what that ends up meaning is sometimes quite mysterious. “Clear and convincing” evidence is said to amount to something like 60-67% probability, maybe even 75% that a given fact or factual scenario is true or false.
In criminal law, a higher standard of proof, called “Beyond Reasonable Doubt” is supposed to be used, but even the Supreme Court has trouble explaining what this means. “Beyond Reasonable Doubt” is said to be a “visceral” (i.e. gut level, almost physical) commitment or “conviction” that a certain fact is true. I suppose that is why the end of a criminal case in which a Defendant is found guilty is called a “conviction.” The jury must be convinced, i.e. have a strong conviction, that the Defendant should be “convicted” of a serious crime which will have much more serious consequences for the Defendant’s life than merely having to pay cash damages for an injury or to stop doing something or be compelled to do something.
The use of vague and imprecise language such as “visceral conviction” and “a deep-seated feeling” that one fact or set of facts is true and another false shows the degree to which “proof” in law is ultimately dependent upon EMOTIONS and “Swaying” the fact-finder one way or another. Both Judges and Juries are counseled to “look into the witnesses eyes” and therein discern whether a witness is “credible” or not.
In short, Law, on which so many things in our lives so absolutely depend, is not rocket science. There are no formulas, there are no easy answers, there are always two sides: “proof” in court is all about emotionally persuading or convincing other people, one jury and up to 12 jurors plus 2 alternates, that your view of the facts is correct and your opponents’ view is wrong. Anyone who disputes the value of emotion in law or legal proof has simply never been to court at all. The jury looks at the parties and looks “up” to the judge for advice and guidance. The Judge looks “down” at the jury and the parties and the witnesses. The Judge “instructs” the jury on the legal guidelines by which to interpret facts. Cases are most often overturned based on the ways in which Judges treat or fail to treat certain facts. But Judges and Juries perceive what lawyers, parties, and witnesses project through non-verbal semiotics things which are neither facts nor matters of proof in any scientific sense.
So, it is not unfair to say that “legal proof” is essentially socially or politically determined IN ALL CASES, and so “legal proof” must be approached as emotionally and passionately as political persuasion or social interaction. A judge or jury exposed only to “facts” devoid of emotion will rapidly fall asleep and be unable to make any decision at all.
“Legal Proof or Persuasion”, then, must be understood as much more a matter of social-psychology, then, and of culturally determined cognition and perception, together with linguistically analyzable argumentative syntax, grammar, semantics, and semiotics, organized in something close to ritually (i.e. dramatically) structured and hierarchical formats, than as “proof” by formula or equation in the scientific or mathematical sense. By extension, “law” is much more social metaphysics than atomic physics.