The question is what level of cogency or conviction should evidence attain before the court can act in favour of the person who bears the burden of proof.
In criminal cases when the burden of proof is on the prosecution the standard of proof is beyond reasonable doubt. The question has arisen as to what is reasonable doubt?
Miller v. Minister of Pensions  2 ALL ER
In this case Lord Denning tried to explain what reasonable doubt would mean he said ‘the degree is well settled. It need not reach certainty, but it must carry a high degree of probability. He continues ‘proof beyond reasonable doubt does not mean proof beyond a shadow of doubt the law would fail to protect the community if it admitted fanciful probabilities or possibilities to deflect the course of justice. If the evidence is so strong against a man as to leave only a remote possibility, in his favour which can be dismissed with a sentence ‘of course it is possible but not in the least probable’, then the case is proved beyond reasonable doubt.’
Lord Denning continues “it must carry a reasonable degree of probability but not as high as is required in criminal cases. If the tribunal can say ‘we think it more probable than not,’ the burden is discharged but if the probabilities are equal, the burden is not discharged. Degree of cogency in burden of proof required is less than in criminal law.
Other people have said that reasonable doubt is the doubt of men of good sense not of imbeciles or fools.
In criminal cases where the accused bears the burden of proof, we have already stated that the standard of proof is on a balance of probability.
The burden of proof in civil matters is on a balance of probabilities.
Where you have cases of fraud for instance if the allegation involves criminal conduct, the degree required is going to be higher. There is a spectrum level of degrees.
R.G. Patel v. Lalji Makanji  E.A. 314
The court in this case stated that allegations of fraud must be strictly proved although the standard of proof may not be so heavy as to require proof beyond reasonable doubt, something more than a mere balance of probabilities.
In a matrimonial offence, there is a variation in the standard of proof. If you are relying on adultery to get your divorce, the standard of proof is beyond reasonable doubt, you have to catch them flagrante delicto.
In Wangari Mathai v. Andrew Mathai it was stated that if you are relying on the offence of adultery the court must prove guilt beyond reasonable doubt or so as to feel sure that the guilt had been proved. The Appellant had argued that there was no direct evidence of adultery and on Appeal it was argued that the degree of adultery had not been proved but the decision was upheld. The court relied on circumstantial evidence to find guilt.