THE INTERPRETATION OF EVIDENCE

• Jurisdiction: Australia

The interpretation of fibres evidence ............................................................ [88C.800]

Assessment of unknown factors ................................................................... [88C.820]

Evidentiary value ........................................................................................... [88C.840]

Data collection and statistical analysis ......................................................... [88C.860]

Conclusion ..................................................................................................... [88C.880]

[88C.800] The interpretation of fibres evidence

In the case example described at [88C.700], several fibres were found which "could have come from" items relating to the complainant on items relating to the suspect and vice versa. Using the test procedures available, no differences were seen which were considered significant.

The question remains: what significance ought to be fairly placed on the "could have come from" statement? While this is a question for the jury, it is the role of the lawyer (prosecution and defence) to ask questions of the scientific witness which will bring out, in a fair and unambiguous way, the weight which can properly be given to the evidence.

Interpreting the value of fibre evidence is the most difficult task facing the scientist. A complete chapter is devoted to the topic in Robertson and Grieve (1999). The reader is referred to this text for a fuller discussion of this topic.

Grieve (1999) gives a list of factors which need to be considered:

(1) Factors that are known (or that can usually be determined):

(a) the circumstances of the case;
(b) the time elapsed before collection of the evidence;
(c) the suitability of the fibre type involved for recovery and comparison;
(d) the extent of comparative information derived from the samples;
(e) the number of types of matching fibres involved;
(f) whether there has been an apparent cross-transfer of fibres;
(g) the quantity or number of recovered matching fibres;
(h) the location of the recovered fibres; and
(i) the methods used to conduct the examination.

(2) Factors that are unknown:

(a) the degree of contact that has occurred and the pressure involved;
(b) the degree of certainty that specific items were definitely involved in contact;
(c) shed potential; and
(d) frequency of occurrence of the matching fibre types.

[88C.820] Assessment of unknown factors

While the unknown factors are difficult to measure, there are a...