Putting this generally, a verdict will be given in favour of the side bearing the legal burden of proof only if, having considered all of the evidence, the fact-finder is satisfied that the applicable standard of proof is met.
The standard of proof has been given different interpretations. On one interpretation, the standard of proof is a probabilistic threshold. The plaintiff will satisfy this standard and succeed in his claim only if there is, on all the evidence adduced in the case, more than 0.
Here the probabilistic threshold is thought to be much higher than 0. Typically, a notional value, such as 0. For the prosecution to secure a guilty verdict, the evidence adduced at the trial must establish the criminal charge to a degree of probability that crosses this threshold.
Kaplan was among the first to employ decision theory to develop a framework for setting the probabilistic threshold that represents the standard of proof. Since the attention in this area of the law tends to be on the avoidance of errors and their undesirable consequences, he finds it convenient to focus on disutility rather than utility. The expected disutility of an outcome is the product of the disutility broadly, the social costs of that outcome and the probability of that outcome.
Only two options are generally available to the court: in criminal cases, it must either convict or acquit the accused and in civil cases, it has to give judgment either for the plaintiff or for the defendant. At a criminal trial, the decision should be made to convict where the expected disutility of a decision to acquit is greater than the expected disutility of a decision to convict.
This is so as to minimize the expected disutilities. To put this in the form of an equation:. P is the probability that the accused is guilty on the basis of all the evidence adduced in the case, Dag is the disutility of acquitting a guilty person and Dci is the disutility of convicting an innocent person.
A similar analysis applies to civil cases: the defendant should be found liable where the expected disutility of finding him not liable when he is in fact liable exceeds the expected disutility of finding him liable when he is in fact not liable. On this approach, a person should be convicted of a crime only where P is greater than:. The same formula applies in civil cases except that the two disutilities Dag and Dci will have to be replaced by their civil equivalents framed in terms of the disutility of awarding the judgment to a plaintiff who in fact does not deserve it and disutility of awarding the judgment to a defendant who in fact does not deserve it.
On this formula, the crucial determinant of the standard of proof is the ratio of the two disutilities. In the civil context, the disutility of an error in one direction is deemed equal to the disutility of an error in the other direction. Hence, a probability of liability of greater than 0. The situation is different at a criminal trial.
Dci , the disutility of convicting an innocent person is considered far greater than Dag , the disutility of acquitting a guilty person. An objection to this analysis is that it is incomplete. It is not enough to compare the costs of erroneous verdicts. The utility of an accurate conviction and the utility of an accurate acquittal should also be considered and factored into the equation Lillquist Ucg is the utility of convicting the guilty, Uag is the utility of acquitting the guilty, Uai is the utility of acquitting the innocent and Uci the utility of convicting the innocent.
Since the relevant utilities depend on the individual circumstances, such as the seriousness of the crime and the severity of the punishment, the decision-theoretic account of the standard of proof would seem, on both the simple and the modified version, to lead to the conclusion that the probabilistic threshold should vary from case to case Lillquist ; Bartels ; Laudan and Saunders ; Ribeiro In other words, the standard of proof should be a flexible or floating one. This view is perceived to be problematic.
First, it falls short descriptively. The law requires the court to apply a fixed standard of proof for all cases within the relevant category. In theory, all criminal cases are governed by the same high standard and all civil cases are governed by the same lower standard. That said, it is unclear whether factfinders in reality adhere strictly to a fixed standard of proof see Kaplow — The argument is better interpreted as a normative argument—as advancing the claim about what the law ought to be and not what it is.
The standard of proof ought to vary from case to case. But this proposal faces a second objection. For convenience, the objection will be elaborated in the criminal setting; in principle, civil litigants have the same two rights that we shall identify. According to Dworkin , moral harm arises as an objective moral fact when a person is erroneously convicted of a crime. Moral harm is distinguished from the bare harm in the form of pain, frustration, deprivation of liberty and so forth that is suffered by a wrongfully convicted and punished person.
While accused persons have the right not to be convicted if innocent, they do not have the right to the most accurate procedure possible for ascertaining their guilt or innocence.
However, they do have the right that a certain weight or importance be attached to the risk of moral harm in the design of procedural and evidential rules that affect the level of accuracy. Accused persons have the further right to a consistent weighting of the importance of moral harm and this further right stems from their right to equal concern and respect.
It is arguable that to adopt a floating standard of proof would offend the second right insofar as it means treating accused persons differently with respect to the evaluation of the importance of avoiding moral harm. This difference in treatment is reflected in the different level of the risk of moral harm to which they are exposed.
There is a third objection to a floating standard of proof. Picinali sees fact-finding as a theoretical exercise that engages the question of what to believe about the disputed facts. Briefly, theoretical reasoning is concerned with what to believe whereas practical reasoning is about what to do.
Only reasons for belief are germane in theoretical reasoning. Decision theory cannot therefore be used to support a variable application of the standard of proof beyond reasonable doubt. The third criticism of a flexible standard of proof does not directly challenge the decision-theoretic analysis of the standard of proof.
On that analysis, it would seem that the maximisation of expected utility is the criterion for selecting the appropriate probabilistic threshold to apply and it plays no further role in deciding whether that threshold, once selected, is met on the evidence adduced in the particular case.
It is not incompatible with the decision-theoretic analysis to insist that the question of whether the selected threshold is met should be governed wholly by epistemic considerations. However, it is arguable that what counts as good or strong enough theoretical reason for judging, and hence believing, that something is true is dependent on the context, such as what is at stake in believing that it is true.
More is at stake at a trial involving the death penalty than in a case of petty shop-lifting; accordingly, there should be stronger epistemic justification for a finding of guilt in the first than in the second case. Philosophical literature on epistemic contextualism and on interest-relative accounts of knowledge and justified belief has been drawn upon to support a variant standard of proof Ho ch. The premise of the third criticism is that the trier of fact has to make a finding on a disputed factual proposition based on his belief in the proposition.
This is contentious. Beliefs are involuntary; we cannot believe something by simply deciding to believe it. The dominant view is that beliefs are context-independent; at any given moment, we cannot believe something in one context and not believe it in another.
On the other hand, legal fact-finding involves choice and decision making and it is dependent on the context; for example, evidence that is strong enough to justify a finding of fact in a civil case may not be strong enough to justify the same finding in a criminal case where the standard of proof is higher. Picinali — Belief and acceptance are propositional attitudes: they are different attitudes that one can have in relation to a proposition.
As Cohen 4 explains:. Understanding standards of proof in terms of mathematical probabilities is controversial. It is said to raise a number of paradoxes Cohen ; Allen , ; Allen and Leiter ; Redmayne Let us return to our previous example.
Leaving aside the reference class problem discussed above, there is a 0. But most lawyers would agree that the evidence is insufficient. Another familiar hypothetical scenario is set in the criminal context Nesson — Twenty five prisoners are exercising in a prison yard. Twenty four of them suddenly set upon a guard and kill him. The remaining prisoner refuses to participate. We cannot in the ensuing confusion identify the prisoner who refrained from the attack.
Subsequently, one prisoner is selected randomly and prosecuted for the murder of the guard. Those are the only facts presented at the trial. The applicable standard is proof beyond a reasonable doubt. Assume that the probabilistic threshold of this standard is 0. On the statistical evidence, there is a probability of 0. In both of the examples just described, why is the evidence insufficient and what does this say about legal standards of proof?
Various attempts have been made to find the answers for surveys of these attempts, see Enoch and Fisher —; Redmayne , Ho —, —; Gardiner b; section 6 of the entry on legal probabilism. It has been argued that meeting a legal standard of proof is not merely or fundamentally a matter of adducing evidence to establish a mathematical probability of liability beyond a certain level. Standards of proof should be interpreted in epistemic rather than probabilistic terms.
According to one interpretation, the evidence is sufficient to satisfy a standard of proof only if it is capable of justifying full or outright belief in the material facts that constitute legal liability and bare statistical evidence, as in our examples, cannot justify such a belief.
Nelkin ; Smith ; Buchak ; Ho 89— Evidence normically supports a proposition just in case the situation in which the evidence is true and the proposition is false is less normal, in the sense of requiring more explanation, than the situation in which the evidence and the proposition are both true. Where all that we have is statistical evidence, it could just so happen that the material proposition is false it could just so happen that the accident-causing bus was red or that the accused was the one who refused to join in the murder , so no further explanation is needed where the proposition is false than where it is true Smith High probability of liability alone will not suffice.
It is further claimed that the relevant knowledge necessary for a finding of liability cannot be obtained from statistical evidence alone Littlejohn and ; Blome-Tillmann ; Moss and forthcoming. An alternative argument is that knowledge requires the ruling out of all relevant alternatives and, to take our prison scenario, there is no evidence that addresses the possibility that the defendant was the one who refrained from joining in the attack or the possibility that the defendant is less likely to be guilty than an arbitrary prisoner in the yard.
See Moss forthcoming; Moss Gardiner a adapts the relevant alternatives framework to model legal standards of proof in a non-mathematical way while eschewing a knowledge account of those standards. Another possible explanation for the failure to know relies on the notion of sensitivity.
The belief that the defendant is liable is not sensitive to the truth where it is based on bare statistical evidence; in the bus example, evidence of the market share of buses remain the same whether it is true or not that a blue bus caused the accident cf. Enoch, Spectre, and Fisher ; Enoch and Fisher ; Enoch and Spectre — while suggesting that the lack of knowledge has generally to do with the insensitivity of the belief, the authors deny that knowledge should matter to the imposition of legal liability.
Yet another explanation is that it is unsafe to find a person liable on bare statistical evidence. Though safety is sometimes treated as a condition of knowledge in that knowledge requires a true belief that is safe , one can treat safety as a condition for finding the defendant liable without also taking the position that the finding must be based on knowledge of liability.
Safety is commonly understood in terms of whether a belief formed on the same basis would be true in close possible worlds.
Roughly, a finding of liability is unsafe where it can easily be wrong in the sense that little in the actual world needs to change for it to be wrong. Whether the requirement of safety can explain why judgment should not entered against the defendant in our two hypothetical cases would depend on whether it can easily happen that the accident-causing bus was red or that the accused is innocent.
See Pritchard and ; Pardo ; cf. Gardiner While theorizing of standards of proof in epistemic terms has gathered pace in recent years, it is criticised for relying on unrealistic hypotheticals that fail to attend to the actual operation of legal systems and for making impossible epistemological demands Allen There is another paradox in the mathematical interpretation of the standard of proof. Imagine a claim under the law of negligence that rests on two elements: a breach of duty of care by the defendant element A and causation of harm to the plaintiff element B.
To win the case, the plaintiff is legally required to prove A and B. For the sake of simplicity, let A and B be mutually independent events.
Suppose the evidence establishes A to a probability of 0. On the mathematical interpretation of the civil standard of proof, the plaintiff should succeed in his claim since the probability with respect to each of the elements exceeds 0.
However, according to the multiplication rule of conventional probability calculus, the probability that A and B are both true is the product of their respective probabilities; in this example, it is only 0.
Thus, the overall probability is greater that the defendant deserves to win than that the plaintiff deserves to win, and yet the verdict is awarded in favour of the plaintiff. So, in our example, the plaintiff should lose since the overall probability is below 0. But this suggested solution is unsatisfactory.
The required level of overall probability would then turn on how many elements the civil claim or criminal charge happens to have. The greater the number of elements, the higher the level of probability to which, on average, each of them must be proved. This is thought to be arbitrary and hence objectionable. As two commentators noted, the legal definition of theft contains more elements than that for murder. Criminal law is not the same in all countries. We may take the following as a convenient approximation of what the law is in some countries: murder is 1 an act that caused the death of a person 2 that was done with the intention of causing the death, and to constitute theft, there must be 1 an intention to take property, 2 dishonesty in taking the property, 3 removal of the property from the possession of another person, and 4 lack of consent by that person.
Since the offence of theft contains twice the number of elements as compared to murder, the individual elements for theft would have to be proved to a much higher level of probability in order for the probability of their conjunction to cross the overall threshold than the individual elements for the much more serious crime of murder Allen and Leiter —5.
This is intuitively unacceptable. Another proposal for resolving the conjunction paradox is move away from thinking of the standard of proof as a quantified threshold of absolute probability and to construe it, instead, as a probability ratio. One criticism of this interpretation of the standard of proof is that it ignores, and does not provide a basis for ignoring, the margin by which one probability exceeds the other, and the difference in probability may vary significantly for different elements of the case Allen and Stein There is a deeper problem with the probabilistic conception of the standard of proof.
There does not seem to be a satisfactory interpretation of probability that suits the forensic context. The only plausible candidate is the subjective meaning of probability according to which probability is construed as the strength of belief. The evidence is sufficient to satisfy the legal standard of proof on a disputed question of fact—for example, it is sufficient to justify the positive finding of fact that the accused killed the victim—only if the fact-finder, having considered the evidence, forms a sufficiently strong belief that the accused killed the victim.
The fact-finder then receives evidence that blood of type A was found at the scene of the crime and that the accused has type A blood. Fifty percent of the population has this blood type. On the Bayesian approach, the posterior odds are calculated by multiplying the prior odds by the likelihood ratio which, as we saw in section 2.
The subjectivist Bayesian theory of legal fact-finding has come under attack see generally Amaya 82—93; Pardo First, as we already saw in section 3. Secondly, the Bayesian theory is not sensitive to the weight of evidence which, roughly put, is the amount of evidence that is available. This criticism and the concept of weight are further explored in section 3. Thirdly, while the Bayesian theorem offers a method for updating probabilities in the light of new evidence, it is silent on what the initial probability should be.
In a trial setting, the initial probability cannot be set at zero since this means certainty in the innocence of the accused. No new evidence can then make any difference; whatever the likelihood ratio of the evidence, multiplying it by zero the prior probability will still end up with a posterior probability of zero.
On the other hand, starting with an initial probability is also problematic. This is especially so in a criminal case. To start a trial with some probability of guilt is to have the fact-finder harbouring some initial belief that the accused is guilty and this is not easy to reconcile with the presumption of innocence. Tribe —; cf. Posner , suggesting starting the trial with prior odds of , criticized by Friedman The problem of fixing the prior probability is said to disappear if we base fact-finding simply on likelihood ratios: Sullivan, 45— Fourthly, we have thus far relied for ease of illustration on highly simplified—and therefore unrealistic—examples.
In real cases, there are normally multiple and dependent items of evidence and the probabilities of all possible conjunctions of these items, which are numerous, will have to be computed. These computations are far too complex to be undertaken by human beings Callen 10— The impossibility of complying with the Bayesian model undermines its prescriptive value. Fifthly, according to Haack, the Bayesian theory has it the wrong way round. The standard of proof should be understood instead in terms of what it is reasonable for the fact-finder to believe in the light of the evidence presented, and this is a matter of the degree to which the belief is warranted by the evidence.
Evidence is legally sufficient where it warrants the contested factual claim to the degree required by law. Whether a factual claim is warranted by the evidence turns on how strongly the evidence supports the claim, on how independently secure the evidence is, and on how much of the relevant evidence is available to the fact-finder that is, the comprehensiveness of the evidence—see further discussion in section 3.
Haack is against identifying degrees of warrant with mathematical probabilities. Degrees of warrant do not conform to the axioms of the standard probability calculus. For instance, where the evidence is weak, neither p nor not- p may be warranted; in contrast, the probability of p and the probability of not- p must add up to 1. Further, where the probability of p and the probability of q are both less than 1, the probability of p and q , being the product of the probability of p and the probability of q , is less than the probability of either.
On the other hand, the degree of warrant for the conjunction of p and q may be higher than the warrant for either. For her general theory of epistemology, see Haack ch. Sixthly, research in experimental psychology suggests that fact-finders do not evaluate pieces of evidence one-by-one and in the unidirectional manner required under the mathematical model Amaya —5. The holistic nature of evidential reasoning as revealed by these studies has inspired alternative theories that are of a non-mathematical nature.
Nance , Friedman Instead, the comparison is of one hypothesis with one or more particular alternative hypotheses as advocated by a party or as constructed by the fact-finder himself.
On this theory, the evidence is sufficient to satisfy the preponderance of proof standard when the best-available hypothesis that explains the evidence and the underlying events include all of the elements of the claim.
Thus, in a negligence case, the best-available hypothesis would have to include a breach of duty of care by the plaintiff and causation of harm to the defendant as these are the elements that must be proved to succeed in the legal claim. To establish the standard of proof beyond reasonable doubt, there must be a plausible explanation of the evidence that includes all of the elements of the crime and, in addition, there must be no plausible explanation that is consistent with innocence Pardo and Allen —; Pardo — The relative plausibility theory itself is perceived to have a number of shortcomings.
However, the theory is sketchy on the meaning of plausibility and the criteria for evaluating plausibility are left largely unanalyzed. One suggested mitigation of this criticism is to place some demand on the epistemic effort that the trier of fact must take for example, by being sufficiently diligent and thorough in constructing the set of hypotheses from which the best is to be chosen Amaya The third criticism is targeted at holistic theories of evidential reasoning in general and not specifically at the relative plausibility theory.
While it may be descriptively true that fact-finders decide verdicts by holistic evaluation of the plausibility of competing explanations, hypotheses, narratives or factual theories that are generated from the evidence, such forms of reasoning may conceal bias and prejudice that stand greater chances of exposure under a systematic approach such as Bayesian analysis Twining ; Simon , ; Griffin A hypothesis constructed by the fact-finder may be shaped subconsciously by a prejudicial generalisation or background belief about the accused based on a certain feature, say, his race or sexual history.
Individuating this feature and subjecting it to Bayesian scrutiny has the desirable effect of putting the generalisation or background belief under the spotlight and forcing the fact-finder to confront the problem of prejudice.
As the relevant evidence at our disposal increases, the magnitude of the probability of the argument may either decrease or increase, according as the new knowledge strengthens the unfavourable or the favourable evidence; but something seems to have increased in either case,—we have a more substantial basis upon which to rest our conclusion.
I express this by saying that an accession of new evidence increases the weight of an argument. This idea of evidential weight has been applied by some legal scholars in assessing the sufficiency of evidence in satisfying legal standards of proof.
Weight is distinguishable from probability. The weight of evidence may be high and the mathematical probability low, as in the situation where the prosecution adduces a great deal of evidence tending to incriminate the accused but the defence has an unshakeable alibi Cohen Conversely, the state of evidence adduced in a case might establish a sufficient degree of probability—high enough to cross the supposed threshold of proof on the mathematical conception of the standard of proof—and yet lack adequate weight.
The defendant is sued by the show organiser for gate-crashing. The mathematical probability that the defendant was a gate-crasher is 0. But, according to the negation principle of mathematical probability, there is probability of 0.
In these circumstances, it is intuitively unjust to find him liable Cohen A possible explanation for not finding him liable is that the evidence is too flimsy or of insufficient weight.
Proponents of the mathematical conception of the standard of proof have stood their ground even while acknowledging that weight has a role to play in the Bayesian analysis of probative value and the sufficiency of evidence. If a party does not produce relevant evidence that is in his possession, resulting in the court facing an evidential deficiency, it may draw an adverse inference against him when computing the posterior probability Kaye b: ; Friedman One criticism of this approach is that, in the absence of information about the missing evidence, the drawing of the adverse inference is open to the objection of arbitrariness Nance What a judge may do to optimize evidential weight is to impose a burden of producing evidence on a party and to make the party suffer an adverse finding of fact if he fails to produce the evidence.
This will serve as an incentive for the party to act in a manner that promotes the interest in evidential completeness Nance , , Cohen suggests that the standard of proof should be conceived entirely as a matter of evidential weight which, on his theory, is a matter of the number of tests or challenges to which a factual hypothesis is subjected to in court.
He offers an account of legal fact-finding in terms of an account of inductive probability that was inspired by the work of writers such as Francis Bacon and J.
Inductive probability operates differently from the classical calculus of probability. It is based on inductive support for the common-sense generalisation that licences the drawing of the relevant inference. Inductive support for a generalisation is graded according to the number of tests that it has passed, or, putting this in another way, by the degree of its resistance to falsification by relevant variables.
The inductive probability of an argument is equal to the reliability grade of the inductive support for the generalisation which covers the argument. Proof beyond reasonable doubt represents the maximum level of inductive probability. This inference is licensed by the generalisation that normally if a stranger is found immediately after a burglary in possession of the stolen object, he intentionally removed it himself.
The defence may try to defeat the inference by showing that the generalization does not apply in the particular case, for example, by presenting evidence to show that the accused had found the object on the street. Typically, rules of evidence are set forth on a state-by-state basis, however, since the Federal Rules of Evidence were established, nearly forty states abide by these regulations. Additionally, judges are not required to strike or restrict violations of evidence rules on their accord, but rather, it is the duty of the defense or prosecution to challenge actions potentially violating rules of evidence.
The premier reason testimony is presented during a trial is to influence the opinion of a judge or jury that is acting as the decider of the facts. Therefore, certain rules and methods for offering testimony in a trial are enforced to ensure a fair trial for defendants. Some of the more notable rules regulating testimony during a criminal trial, include:.
Expert statements or testimony can be entered into a trial, which may include personal opinions and references to previous testimony of other witnesses. Additionally, expert witnesses can be paid for their time in court.
Prosecutors typically already have experts in various fields on payroll prior to a trial, but an indigent defendant with court-appointed counsel can obtain expert testimony at no cost if the presiding judge feels that without the expert, a fair trial will not prove possible.
The "chain of custody" rules regulate the admissibility and credibility of evidence during a trial to ensure evidence was not tampered with or somehow altered prior to trial. Scientific evidence, or forensic evidence, is information derived through the "scientific method".
Commonly, scientific evidence, such as DNA, fingerprints, ballistics, and other items, is regularly entered during a criminal trial by both sides. Contrary to some beliefs, polygraph evidence is not typically deemed reliable enough to be admitted to a criminal trial, nor are most statements made under hypnosis or other forms of altered consciousness.
The court will admit evidence if it is relevant, material, and competent, and not excluded by the evidence rules. Irrelevant evidence is never admissible. Relevancy is the idea that a piece of evidence is admissible only if connected to the case. Evidence is relevant if it tends to prove or persuade the judge or jury that some fact is true or untrue.
Relevant evidence may include minor issues of the case, such as background information for the parties and witnesses address, age, marital status, etc. Federal Rule of Evidence also includes a materiality standard for admissible evidence. The concepts of relevancy and materiality are similar and often confused, but there is a distinction. For example, an auto insurance company may accept liability but dispute the damages amount claimed.
At trial, the insurer may object that evidence addressing liability is immaterial. The court may refuse to admit relevant and material evidence if a specific rule, regulation, or statute excludes the evidence. But you should know that they exist and can impact what evidence you offer at trial.
The judge decides the admissibility of evidence if the opposing party objects. This includes whether an expert witness is qualified or a privilege exists. Courtroom evidence is either direct or circumstantial. Direct evidence comes from a witness who experienced it directly eyewitness testimony or a document or item that speaks for itself damaged car, medical record, etc.
Circumstantial evidence, also called indirect evidence, is the testimony, documents, or videos that allow the fact finder to conclude that some other fact or event happened. You can use four types of evidence when communicating information to the judge or jury at trial: Testimonial Proof, Documentary Evidence, Demonstrative Evidence, and Real Evidence. Testimony is the most common form of evidence offered in the legal system.
It involves a person taking an oath or affirmation under penalty of perjury before answering questions about matters they observed or know. An expert witness is a person with specialized knowledge, skill, and experience in scientific, technical, or professional issues relevant to the case. Usually an expert witness does not testify about facts. Expert witnesses are necessary for almost all medical malpractice lawsuits. A lay witness is any person who testifies at trial but not as an expert witness.
They must have personal knowledge of the matter to give fact testimony. Testimony may be oral or written.
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