Aficianados of television or big-screen courtroom dramas will be familiar with the term "hearsay evidence" and so will close observers of real crime and the New Zealand justice system.
In two high-profile cases in recent months this legal nicety has been perceived, in one instance by members of the public and in another by the highest court in the land, possibly to have played a conspicuous role in the outcome of trials.
Just this week, the Supreme Court has given leave for an appeal to be heard by the Crown against the acquittal of George Evans Gwaze on two counts of sexual violation and one of murder.
Mr Gwaze had been found not guilty in May 2008 in the High Court at Christchurch following a defence case in which hearsay evidence was allowed to be presented.
The Crown appealed the conviction in the Court of Appeal in July this year, essentially on an admissibility of evidence issue.
The court dismissed it in a majority two-to-one decision in September, following which the Crown sought leave from the Supreme Court.
Its success means that the prosecution will now put its appeal to the full bench of the Supreme Court in late February next year, as a result of which the original acquittal will be upheld or a retrial directed.
Earlier this year, in the retrial of David Bain (following a Privy Council ruling) for the murder of the five members of his family - of which crimes he was acquitted - the jury heard his father Robin Bain was having an incestuous affair with his daughter Laniet.
Because the affair was about to come out, the court heard, he had a motive to kill his family.
Some time after the end of the trial, Robin Bain's brother Michael spoke out about the ruin of his sibling's reputation, stating that the allegations of incest were not based on fact, but were "hearsay".
Other observers, less concerned about Robin Bain's reputation and more interested in the larger question of whether justice had been served in the retrial, wondered if the judge at the original Bain trial had not got it right when he ruled out admissibility of the hearsay "incest testimony" on the basis that it was unreliable.
Since the Crown has not pursued that point and there has been no suggestion that the presiding judge, Justice Graham Panckhurst, erred in law in this matter, it remains a moot point.
The Gwaze case, however, in at least allowing for the possibility of a retrial for a person already acquitted on the charges for which he could now be retried, appears to break new, or at least rarely tilled, ground.
Broadly speaking, hearsay evidence is evidence that has been reported to a witness by another, or others, rather than evidence that he or she has personally observed or heard.
For example, in relation to the Bain case, the witness Dean Cottle alleged in statements - made to the police in 1994 and 1995 and read to the retrial jury by Justice Panckhurst - that Laniet Bain had told him her father was having an incestuous relationship with her.
It was not something he knew of personally from having witnessed it.
As Michael Bain said, neither his brother Robin nor Laniet were around to contradict such evidence or to offer alternative explanations.
In the case of Mr Gwaze, evidence was allowed to be admitted to the trial when one expert witness spoke to a colleague with expertise in the condition of the deceased, an HIV-positive niece of Mr Gwaze whom, the Crown contended, had been raped and suffocated.
The expert witness thought that the evidence, albeit hearsay, was sufficiently pertinent to bring to the attention of the police, and it was subsequently revealed to the defence and to the trial judge.
After complex arguments canvassing its admissibility, the evidence was heard.
Following the acquittal and at appeal, the Court of Appeal considered the trial judge had not erred in law and, with consideration of the "double jeopardy" rule whereby the general disposition of the law has been that those acquitted of a crime should not be retried for it, dismissed the Crown's application.
It would be premature to draw inferences from the fact that the Supreme Court has now given leave for the appeal to proceed, beyond the matter hanging upon a complex set of finely balanced legal nuances.
One possibility, should the Supreme Court find in favour of the Crown, is however a very real dent in the "double jeopardy" principle, with the prospect - an unsettling echo of the constant "retrying" of controversial cases in the media today - of never truly arriving at a final verdict.
On the other hand, without wishing to prejudge the matter, some clarification or firmer rulings on hearsay evidence, and on the precise circumstances in which it can be admitted to the court, might be considered likely to bolster public confidence in the New Zealand legal system.