Opinion and expert evidence

Opinion evidence rule

Witnesses are prohibited from giving their opinions in court. Their testimony should be limited to facts. Thus, they must limit their testimony to what they have seen, heard and experienced

The reasons behind the Opinion evidence rule

The judge and the jury and supposed to draw their oen conclusion from the presented facts.

• If the witness gives his opinion then the jury might be wrongfully influenced and unable to draw an “objective conclusion”

• The witness’ opinion is not more valuable than anyone else’s

Exceptions - Opinion evidence rule

1. Expert opinion evidence

2. Non-expert opinion evidence

Why is expert opinion evidence necessary?

When the evidence presented is too complicated for the jury to understand without the expert giving his opinions

• Letting an expert present complex findings/evidence without allowing them to give their opinion would be pointless

Who is “expert”

Gavin v Murray - “A person whose qualifications give an added authority to pinions or statements given or made by him within the area of his expertise”

• Not confined to those with a university degree or any actual expert qualifications

In some professions, like psychology (that are inexact sciences), the court looks at expert witnesses with certain skepticism (Haines v Bellissimo)

• Hard to draw a line between “normal” and “abnormal”
  
  Doctors, forensic scientists, an engineer, a historian or any other profession

What must the defense do when when wanting to call an expert

• Must ask the court for permission

• Must give notice to the prosecution at least 10 days in advance of the trial date

• (Criminal procedure Act 2010)

Is the jury/judge bound by the expert’s opinion?

No!

• This is almost also expert witnesses on both sides contradicting each other

• The jury is free to pick one side or disregard the opinion of the expert on both sides

Can the accused intention or lack of intention be subject to expert evidence?

No - (DPP v Kehoe)

However, expert evidence is admissible to show that the accused lacked the capacity to form the necessary intention. 

• A difference between intention and the capacity to intend (R v. Toner)

When is expert opinion evidence necessary?

1. When the court has to deal with matters outside of the ordinary knowledge of the jury

2. When the witness possesses specialised knowledge that may assist the jury in reaching their verdict.

(If it is concluded that an expert opinion is unnecessary then the “Opinion Evidence Rule” kicks in and the witness is not allowed to give its opinion.)

Common knowledge rule

If the evidence given by the experts lies within the expertise of a normal person then the expert evidence is unnecessary. (R v. Anderson and Neville)

But, sometimes you need an expert’s opinion regarding how some things are seen/interpreted by a certain group pf people in society, for example children (DPP v. A and BC Chewing Gum)

Non-expert opinion evidence

Non-expert evidence is admissible in circumstances where it is impossible to separate fact from opinion

• HOWEVER: The line between fact and opinion is not often super clear. And fact is often based on an opinion (ex. old, young, tall, short, size of a crowd and the emotional state of a person etc.)

Where do we draw the line between fact and opinion?

Lord MacDermott: The following can be allowed:

• Identification of persons and things

• Apparent age

• Bodily condition

• The emotional state of a person

• Condition of items (new/old etc)

• Questions of valur

• Estimates of speed or distance

The ultimate issue rule

When a witness is giving evidence, they cannot give their opinion on the ultimate issue in the case:

• Criminal case = The thing that has to be proven / disproven in order for the accused to be found guilty

• Civil case = The thing that has to be proved / disproved for a party to win the case

(The people (DPP) v. Razman)