Defamation : Evidence of Character and Reputation.
If for example you were a thief and had been convicted of such an offence, but then accused wrongly of an offence against children, or a sexual offence, then it would still be possible to sue for libel despite your existing bad reputation because it could be argued that the publication had lowered your reputation further.
If however an allegation is made against you in a similar vein for example if you have been convicted of a theft offence and then you were wrongly accused of another theft offence it would be difficult to show that your reputation had been lowered further in the estimation of right thinking people.
In the case of Scott v Sampson (1882) 9QBD 491 the court was concerned with evidence that might be called by the defendant in relation to the character of the Claimant,
“Speaking generally the rule recognised is that every man has a right to have the estimation in which he stands in the opinion of others unaffected by false statement to his discredit; and if such false statements are made without lawful excuse, and damages results to the person to whom they are made, he has a right of action.”
That case means that a defendant cannot revert to the claimants poor character unless there are examples of the defendants misconduct being raised as justification.
The case of Burstein v Times Newspapers Limited sets out the position when libel has been committed, background evidence relevant to the publication of the statement can be used to argue that damages should be reduced.