Of Evidence

All evidence is to be weighed according to the proof which was in the power of one side to have produced, and in the power of the other to have contradicted'.
Per Lord Mansfied in Blatch v Archer [1774] EngR 2; (1774) 1 Cowp 63

Briginshaw v Briginshaw [1938] HCA 34; (1938) 60 CLR 336 per Dixon J

Citing from Starkie's Law of Evidence;
"It is to be observed, that the measure of proof sufficient to warrant the verdict of a jury varies much, according to the nature of the case.
Evidence which satisfies the minds of the jury of the truth of the fact in dispute, to the entire exclusion of every reasonable doubt, constitutes full proof of the fact; absolute mathematical or metaphysical certainty is not essential, and in the course of judicial investigations would be usually unattainable. Even the most direct evidence can produce nothing more than such a high degree of probability as amounts to moral certainty. From the highest degree it may decline, by an infinite number of gradations, until it produce in the mind nothing more than a mere preponderance of assent in favour of the particular fact. The distinction between full proof and mere preponderance of evidence is in its application very important. In all criminal cases whatsoever, it is essential to a verdict of condemnation that the guilt of the accused should be fully proved; neither a mere preponderance of evidence, nor any weight of preponderant evidence, is sufficient for the purpose, unless it generate full belief of the fact to the exclusion of all reasonable doubt" (1st ed. (1824), pp. 450, 451; 4th ed. (1853), pp. 817, 818).

When, however, he [Starkie] passes to the standard of proof in other cases, he describes it in less positive and definite terms (1st ed. (1824), p. 451; 4th ed. (1853), p. 818):

"...But in many cases of a civil nature, where the right is dubious, and the claims of the contesting parties are supported by evidence nearly equipoised, a mere preponderance of evidence on either side may be sufficient to turn the scale. This happens, as it seems, in all cases where no presumption of law, or prima-facie right, operates in favour of either party; as, for example, where the question between the owners of contiguous estates is, whether a particular tree near the boundary grows on the land of one or of the other. But even where the contest is as to civil rights only, a mere preponderance of evidence, such as would induce a jury to incline to the one side rather than the other, is frequently insufficient. It would be so in all cases where it fell short of fully disproving a legal right once admitted or established, or of rebutting a presumption of law."

This mode of stating the rule for civil issues appears to acknowledge that the degree of satisfaction demanded may depend rather on the nature of the issue.

...The truth is that, when the law requires the proof of any fact, the tribunal must feel an actual persuasion of its occurrence or existence before it can be found. It cannot be found as a result of a mere mechanical comparison of probabilities independently of any belief in its reality. No doubt an opinion that a state of facts exists may be held according to indefinite gradations of certainty; and this has led to attempts to define exactly the certainty required by the law for various purposes. Fortunately, however, at common law no third standard of persuasion was definitely developed.

Except upon criminal issues to be proved by the prosecution, it is enough that the affirmative of an allegation is made out to the reasonable satisfaction of the tribunal. But reasonable satisfaction is not a state of mind that is attained or established independently of the nature and consequence of the fact or facts to be proved. The seriousness of an allegation made, the inherent unlikelihood of an occurrence of a given description, or the gravity of the consequences flowing from a particular finding are considerations which must affect the answer to the question whether the issue has been proved to the reasonable satisfaction of the tribunal. In such matters "reasonable satisfaction" should not be produced by inexact proofs, indefinite testimony, or indirect inferences. Everyone must feel that, when, for instance, the issue is on which of two dates an admitted occurrence took place, a satisfactory conclusion may be reached on materials of a kind that would not satisfy any sound and prudent judgment if the question was whether some act had been done involving grave moral delinquency.

It is often said that such an issue as fraud must be proved "clearly", "unequivocally", "strictly" or "with certainty" (Cf. Mowatt v. Blake[41]; Kisch v. Central Railway Co. of Venezuela Ltd.[42]; Lumley v. Desborough[43]). This does not mean that some standard of persuasion is fixed intermediate between the satisfaction beyond reasonable doubt required upon a criminal inquest and the reasonable satisfaction which in a civil issue may, not must, be based on a preponderance of probability. It means that the nature of the issue necessarily affects the process by which reasonable satisfaction is attained.

It is a well-known principle of our jurisprudence that the party who alleges misconduct against another is bound to establish such misconduct by affirmative evidence. Unless, therefore, it is proved to the satisfaction of the court, that the respondent has been guilty of the misconduct imputed to her, it is bound to dismiss the petition.

[On circumstantial evidence]

The language used by more than one of their Lordships in�Ross v. Ross[67] shows, I think, that satisfaction beyond all reasonable doubt is not the criterion applied where proof of adultery depends on circumstances. For, if that had been the accepted test, it would indeed be strange if it were not applied or relied upon as part of the reasons for holding, as a majority of the House of Lords did, that the circumstances failed to establish guilt. So far from applying this standard, Lord�Buckmaster�first speaks of proof of adultery "as a matter of inference and circumstance" and then, in denying the sufficiency of the fact that the parties are thrown together in an environment which lends itself to the commission of the offence, states the necessary qualification thus: "Unless it can be shown ... that the association of the parties was so intimate and their mutual passion so clear that adultery might reasonably be assumed as the result of an opportunity for its occurrence"[68]. Lord�Atkin, alluding to the circumstances telling in favour of innocence, says simply: "Such a charge in such circumstances ought to be fully proved"[69]. Lord�Thankerton�said: "Admittedly the respondent must prove facts which are not reasonably capable of an innocent construction"[70].

Findings based on credibility

SMART -v- POWER [2019] WASCA 106
http://www6.austlii.edu.au/cgi-bin/viewdoc/au/cases/wa/WASCA/2019/106.html?query=#fn124
104.In the case of a finding that is based, at least to any substantial degree, on an assessment of the credibility of one or more witnesses, an appellate court will not interfere with the finding unless it is demonstrated to be wrong by reference to incontrovertible facts or uncontested testimony, or because the finding is glaringly improbable or contrary to compelling inferences, or because the trial judge failed to use, or has palpably misused, their advantage as trial judge.[124]

Credit - Phipson on Evidence at 470 et seq
Knowledge Observation, memory

The credibility of a witness depends upon his knowledge of the facts - his intelligence - his disinterestedness - his integrity - his veracity

Knowledge Observation, Memory

Obvious matters affecting the weight of a witness's evidence may be are:

- his means of knowledge
- opportunities of observation
reasons for recollection or belief
experience
powers of memory and perception
any special circumstances affecting his competency to speak to the particular case
all of which may be enquired either in XN to enchance or in XXN to impeach the value of the testimony
Errors, Omissions etc
Antecedence, Associations, Character etc