[ 33] The defence focused on the possibility of human error, not
on the technicalities of the mechanical tracing process. The
defence argued that because significant parts of the process
depended upon whether individuals properly followed procedures
and accurately recorded and reported data, the accuracy of the
system could not be properly assessed, absent both evidence from
those individuals and the relevant records. The jury did not need
a detailed explanation of the tracing process to properly understand the thrust of the “human error” arguments advanced on
behalf of the appellant.
[ 34] The trial judge could have gone into the details of the evidence. Some trial judges would have done so. In those cases, this
court might be hearing an argument about the confusion created
by an unnecessarily detailed summary of evidence that had little
to do with the defence challenge to the reliability of the evidence.
The trial judge’s decision to give a general but even-handed
summary of the tracing evidence did not amount to an error in
law. Nor did it render the instructions unfair.
[ 35] The specific factual inaccuracies alleged by the appellant
are more in the nature of incomplete descriptions of the evidence.
In my view, none are significant and none would have misled the
jury on the substance of the tracing evidence or the defence position in respect of that evidence.
(b) The review of the defence position
[ 36] I must also reject the argument that the trial judge failed
to adequately put the defence position with respect to the tracing
evidence forward and instead wrongly suggested to the jury that
the evidence established that the process was almost always accu-
rate. While the appellant is correct that the trial judge made two
references to Mr. Johnston’s evidence that the tracing process
was 99.9 per cent accurate, the jury could not, in the context of
this case, have understood the trial judge to be referring to both
the mechanical and human components of the tracing process. It
was made clear in cross-examination that Mr. Johnston could not
speak to the accuracy of the human component of the process. In
closing submissions, counsel made the same point in referencing
Mr. Johnston’s evidence:
The tracing procedure falls into two basic categories: mechanical steps and
human steps. The mechanical steps are indeed highly reliable, and that’s
what Mr.Johnston meant when he talked about the tracing being
ninety-nine-point-nine percent accurate. I asked him. I said, “You’re
talking about what the machines do.” He said, “That’s right.” “You’re not
talking about what the humans do.” He said, “No.”