"In the absence of statute law, the whole matter must
at present turn in New Zealand on the wide jurisdiction
to develop the rules of evidence and to prevent
unfairness in criminal trials - a jurisdiction
discussed recently in Busby v Thorn EMI Video
Programmes Ltd (1984) 1 NZLR 461, 471-473.
...
Obviously the greater the safeguards, the greater the
likelihood that the evidence will be admitted. For,
unless the hypnosis has been accompanied by safeguards
which the Judge considers reasonable in the particular
circumstances, it may become necessary to exclude even
evidence of the subject's pre-hypnotic recollections.
And when objection is made to any post-hypnotic
evidence, a voir dire hearing will be necessary before
or during the trial.
Accordingly we hold that in all cases where the Crown
proposes to call post hypnotic testimony:
1 The fact that the witness was hypnotised should be
disclosed to the defence, and all relevant transcripts
and information provided on request.
2 If objected to, the evidence should be excluded
unless the Judge is satisfied that it is safe to admit
it in the particular circumstances.
3 The Judge should have regard to whether the
hypnotism was carried out by a qualified person
independent of the police and the prosecution, and with
sufficient safeguards against the influencing of the
subject by suggestions or otherwise.
4 Pending the establishment of New Zealand guidelines,
in deciding whether safeguards are sufficient reference
may be made to overseas guidelines, such as the
Californian section set out in this judgment. They are
not mandatory in New Zealand but indicate standards to
be aimed at as far as reasonably possible.
5 The Judge should also have regard to the strength of
any confirmatory or supporting evidence to be called by
the Crown. This applies in all cases but is especially
important in relation to any recollection or purported
recollection which is not proved by the Crown to have
existed before hypnotism.
6 If he admits the evidence, the Judge should warn the
jury of the special need for caution before relying on
post-hypnotic evidence. The warning need not be in any
particular terms but should adequately alert the jury
to the dangers referred to in this judgment.
It will be apparent from what we have said that while
hypnotism may occasionally be valuable, even essential,
as an investigative technique, its use on a potential
witness should never be embarked upon without careful
consideration of the evidential risks. What we have
said has necessarily been concerned with hypnotism of
Crown witnesses. In general, however, the same
approach must apply as regards defence witnesses."