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Flashcards in Expert (Opinion) Evidence Deck (40):

What is the distinction made between fact and opinion in the law of evidence?

There is a distinction in the law of evidence between: 1) fact and 2) opinion. Generally speaking the court's are not interested in opinions. The general rule is that opinion evidence is inadmissible:
⁃ "The general rule is that it would be quite wrong and inadmissible to put a witness into the witness box to tell the jury what the evidence they have been listening to ought to convey to them." (*Hopes and Lavery v HM Advocate 1960)


What is the rationale for the general rule that opinion evidence is inadmissible?

Such evidence is unnecessary and might even confuse matters.

Such evidence usurps the function of the factfinder.


What are the exceptions to the general rule?

1) The first exception: evidence of "an impression formed at the time of the incident"
2) The second exception: "expert" witnesses can give evidence of opinion
3) The "actual issue" rule
4) Questions of ordinary human nature and behaviour


What is the rationale for the exception of evidence of "an impression formed at the time of the incident"?

Perhaps that it is not possible readily to separate fact from opinion in this regard; allowing this type of opinion evidence does not give rise to the sorts of problems that a more general relaxation of the prohibition might.


King v King (1842)

Civil case. An action for divorce on the ground of adultery. The court held that it was acceptable to ask a witness about the immediate impression she had formed when she entered the room and saw the defender and another in a compromising position because what the court was concerned with was the impression that had been formed when she saw the person. She was being asked what she saw and what she thought was going on.


Wilson v Wilson (1898)

Another actions for divorce on the ground of adultery. In this case the only direct witness to the alleged adultery was a lamp lighter working in the tenement stair where the alleged incident was said to have happened. He saw the defender and the person with whom he was supposed to be committing adultery lying side by side in the stair and he said that he couldn't expect that they were there for anything except immoral purposes. [This case is a good example of how fact and opinion can sometimes be very similar - the line is often blurred.]


Hewat v Edinburgh Corporation 1994:

Civil case trying to sue for falling and injuring in the street. Held: whether the hole can be considered dangerous is a question which can properly be put to a police constable as they have a duty to report on matters of dangerous public road conditions.


What is the second exception of "expert" witnesses can give evidence of opinion?

Generally expert opinion evidence is admissible. It is allowed in order to try and help the jury to make sense of the information that they have before them, particularly when issues are specialist and outside everyday experience or common knowledge.


What is the function of the 'expert'?

The function of the expert is "to furnish the judge and jury with the necessary scientific criteria for testing the accuracy of their conclusions, so as to enable the judge or jury to form their own independent judgement by the application of these criteria to the facts proved in evidence." Davie v Magistrates of Edinburgh 1953 per the Lord President (Cooper).


What can the expert not do?

The expert cannot usurp the role of the fact finder. They are only trying to assist and help jury to understand the evidence. They cannot tell them which decision to come to based on that evidence.


What are the type of facts that an expert might give evidence on?

⁃ Tests that they've conducted
⁃ Causes of death
⁃ Ballistics
⁃ Etc etc etc


Is there an automatic right to call an expert?

There is no automatic right to call an expert:
⁃ The evidence must be relevant and appropriate in the circumstances, otherwise it will be excluded. Generally speaking where the issue is one of normal human behaviour or human nature then jurors will be expected to have the requisite experience to be able to decide these issues alone:


*R v Turner [1975]

(Not very good explanation - look up)
⁃ The defendant had been charged with murder. He had admitted killing his girlfriend with a hammer but he claimed he had been provoked by her statements that she had had affairs with other men and he wasn't the father of the child that she was expecting. The defendant's lawyer tried to bring in evidence that the defendant was not suffering from a mental illness so that he could bring in psychiatrists to give evidence on the matter - he wanted psychiatrists to argue that he was not violent by nature but his personality was such that in these circumstances he would have been provoked.
⁃ The Crown objected to this evidence being admitted and asked for it to be excluded because the reason the defence wanted it admitted was to try and suggest that the character of the defendant was non-violent when in actual fact the defendant had a history of violence.
⁃ The judge held that expert psychiatric evidence was inadmissible since the question of whether the defendant was suffering from a mental illness was not an issue and thus the evidence was excluded - the issue of whether he was provoked or not was something which is in the competence and experience of the average juror.
⁃ In making this decision the court set out a more general position about expert opinion evidence - that if it is relevant and is not based on hearsay then it is admissible.
- Rule: no automatic right to call an expert


When is an expert necessary?

Scientific or technical nature.

An example to illustrate when expert evidence is necessary is: R v Stockwell (1993)


R v Stockwell (1993)

⁃ A video was taken by a security camera and the video showed a man robbing a building society. Some months later an attempted robbery took place at another building society and was caught on video camera. The appellant was charged with both of these offences but denied involvement in either crime. The main issue in the trial was determining who had carried out the crimes (identification). At the trial stage the judge ruled that evidence of a facial mapping expert was admissible to try to assist in determining whether the appellant was actually the person who appeared in the videos. The accused was convicted.
⁃ On appeal he argued that the judge had made a mistake in ruling the way he did because the jury ought to have been capable of deciding themselves whether the accused person was the same person as appeared in the CCTV footage. A facial mapper could have been helpful where the accused was disguised. Expert evidence was held to be admissible. The court emphasised that there is no reason for the jury to be bound by the expert evidence.
⁃ The appeal was dismissed on the basis that in cases where identification is an issue and in cases like this the accused was perhaps disguised, there is not reason why expert evince should not be allowed.
⁃ [Thus expert evidence was thought to be essential in determining who committed these offences. But it was also stressed that the jury should be told that they were not bound by this opinion.]


What is the "actual issue" rule?

This rule is either known as the 'actual'/'ultimate' issue rule. This rule states that an expert witness should only assist the trier of fact to decide on the ultimate issues (e.g. the guilt of the accused / liability of the defender). This is intended to avoid usurpation of the function of the court.


Galletly v Laird 1953

⁃ Person convicted of trafficking indecent or obscene publications and wanted to have his conviction suspended on a number of grounds, one of which was that the magistrate had rejected evidence that showed that books of a similar character to those that he was dealing in were considered decent by responsible members of the community - so the appellant was trying to argue that expert evidence would have confirmed that the books were not deemed to be obscene but normal members of society
⁃ The court held that this was not a case where expert evidence was to be admitted - it was a case for the magistrate to observe the materials himself and decide if they were obscene, so other people's views were irrelevant here.
⁃ [So because obscenity was thought to be within the realm of ordinary people's experience the expert evidence was held to have been rightly excluded.]


Hendry v HM Advocate

This case makes it clear that expert evidence must not be the determining factor in the ultimate issue.

⁃ Homicide case. Accused had been charged with assaulting an elderly man after he knocked him over and kicked him and the man had a heart attack and died. The question was one of causation since he had an underlying heart problem etc. Medical witnesses were brought into the court to testify as to whether the assault had caused the heart attack or there were other factors which could have caused it. They argued that they couldn't say beyond reasonable doubt that the heart attack was caused by the accused so he shouldn't be convicted. But despite this evidence the accused was convicted. He appealed on the ground that there wasn't enough medical evidence to prove causation.
- Expert was being asked to speculate on the cause of death. In the course of the trial the expert gave his opinion that the victims poor health meant there was reasonable doubt over whether the kicking had caused the death. The victim was convicted on culpable homicide, and appealed.
⁃ The court held that it wasn't for the expert witness to decide this - it was to be determined by the trier of fact (the jury). [Thus this emphasises again that the ultimate issue is to be decided by the trier of fact.]
- Expert is not allowed to throw doubt on whether the attack caused the death this is a matter for the jury to decide beyond reasonable doubt.


But what if an expert witness adopts the language of the legal test?

See e.g. the definition of diminished responsibility offered in Galbraith v HM Advocate (No 2) 2002
⁃ The appellant was charged with murdering her husband after a number of years of abuse in which she was suffering from PTSD. The argument was that she should be convicted only of culpable homicide on the basis of diminished responsibility. She was convicted of murder and appealed. On appeal she argued that the jury should have been directed that they could return a verdict of culpable homicide if they accepted the evidence of abuse and the psychologists evidence that she was suffering from PTSD (from the effects of the abuse). However the court held that diminished responsibility was a legal concept (thus not a medical concept) so it is not for expert witnesses to decide.
⁃ So while the expert witnesses can and should give evidence as to the mental state of the accused, the ultimate legal question of whether this mental state satisfies the requirements of the legal test of diminished responsibility has to be decided by the judge or the jury[ This reflects the fact that in some cases the sorts of language that is used by expert witnesses and by the judge in directing the jury can sometimes sound very similar and can possibly lead to confusion as to exactly what weight should be afforded to the expert evidence.

Put simply the expert witnesses must only give evidence as to the factual circumstances since they are only their to assist.].
- Expert is not allowed to translate medical facts into the legal outcome of whether she had diminished responsibility is one for the jury to make.


Cf: Ingram v Macari 1983

⁃ Shopkeeper charged with conducting himself in a shamelessly indecent manner - he was charged with selling indecent magazine. At the trial the sheriff had allowed evidence to be given for the defence by a psychologist and psychiatrist on the effects of pornography. They said that in this case these magazines were not likely to corrupt the morals of those people reading them so the accused should be acquitted. On appeal the court held that the issue of whether the magazines were likely to corrupt the morals of those reading them was for the sheriff alone.


What are the questions of ordinary human nature and behaviour?

Expert witnesses cannot give evidence on questions of ordinary human nature and behaviour:
⁃ "The fact that an expert witness has impressive scientific qualifications does not by that fact alone make his opinion on matters of human nature and behaviour within the limits of normality any more helpful than that of the jurors themselves; but there is a danger that they [the jury] may think it does." (*R v Turner [1975] QB 834 per Lawton LJ).

One specific application of this principle is the rule against oath-helping.


What is the rule against oath-helping?

This rule prevents a person from leading evidence to enhance the credibility of his or her own witnesses.


*HM Advocate v Grimmond 2002

⁃ In this case the accused was charged with sodomy against 2 young boys. At trial the Crown had tried to lead evidence from a child psychologist to the effect that the statements made by these boys were credible and reliable. The psychologist hadn't had any contact with the children - he was simply making this assessment on the basis of material that had been provided to him. The accused objected to the use of this expert evidence stating that the credibility of the children was really a matter for the jury to decide.
⁃ The court held that evidence relating to the credibility of a witness (aside from evidence given by the witness themselves) is generally inadmissible unless it is also relevant to other questions that are in issue. e.g. So if there is a suggestion that a witness has suffered from some kind of mental disorder which has an impact on his or her credibility then possibly expert evidence may be admissible in this situation (but if the only purpose of the evidence is to establish the credibly of the witness then generally it is inadmissible.) In this case since the children were ordinary children the decision as to their credibility was to be made by the jury.


AJE v HM Advocate 2002

This case suggests that this rule against bringing evidence to establish credibility is weaker than it once was.

⁃ Man charged with raping his two young daughters over a period of several months. The girls gave evidence at the trial and the Crown sought to lead evidence of the girl's behavioural difficulties and prior statements they'd given on this matter. They also led evidence of a social worker (who is classed as an expert witness) which suggested that in her opinion small children could give reliable evidence of sexual abuse even if they previously denied that it happened or had given inconsistent statements.[ So this was expert evidence to try to establish that even if previous statements of these children were inconsistent with what they were saying when they were giving evidence - this didn't necessarily mean that they couldn't be trusted.]
⁃ The accused was convicted and appealed. The appeal was allowed on the ground that the appellant's defence counsel had decided not to pursue various other avenue's that the accused had asked him to (including evidence which would have had a bearing on the Crown's expert opinion evidence). This evidence that the accused had wanted to bring into the trial was evidence that perhaps the children had been manipulated in some way (i.e. techniques used when children were interviewed) but these issues weren't explored because the defence lawyer never brought them to the court's attention. The appeal was successful because these avenues weren’t explored.
⁃ So the court held that there was no way of knowing what the outcome would have been if this other expert evidence had been introduced but the fact it wasn't sought out meant that his appeal was allowed. So perhaps the expert evidence would have been admissible to challenge the credibility of the child witnesses. Therefore this case suggests that the rule against oath helping may be slightly weaker than it once was.


*HM Advocate v A 2005

Expert evidence was allowed for this purpose. Concerns s 275 CPSA 1995[ When there is a sexual offence being tried - if an application is made under s 275 and is successful then this allows questions to be asked which show that a person is not of good character.]. The accused was charged with lewd, libidinous and indecent practices against two young girls. Applications were made under s 275 of the Act. One of these was successful. This meant that evidence was brought in that showed the girl had given two statements to the police claiming she had been abused but these two statements were inconsistent. The defence lawyer called on an expert witness who was a consultant psychiatrist who came to the conclusion after considering the statements of the child and after looking at her medical records that shew as suffering from 'false memory syndrome' which was linked to a mental illness which preceded her allegations of abuse. In response the Crown wanted to lead evidence from a different expert witness - a clinical psychologist who supported the theory that the child's memory had been repressed as a result of sexual abuse and dealing with traumatic memories.
⁃ The accused tried to object to the Crown leading this expert evidence because the reason the Crown are bringing this evidence to the court's attention was to bolster the girls credibility (i.e. it was contrary to the general rule against oath-helping).
⁃ The court held that in order to understand a girl's state of mind and reach a conclusion on the reliability and credibility of her as a witness the jury needed expert evidence - the general rule against oath-helping was trumped by the duty of the court to ensure that the trial was conducted fairly.


How are sexual offence cases now dealt with?

The situation in sexual offence cases like HM Advocate v A 2005 (above) is now dealt with by the CPSA 1995 s 275C (inserted by the Vulnerable Witnesses (Scotland) Act 2004): in sexual offence cases, "[e]xpert psychological or psychiatric evidence relating to any subsequent behaviour or statement of the complainer is admissible for the purpose of rebutting any inference adverse to the complainer's credibility or reliability as a witness which might otherwise be drawn from the behaviour or statement.."


Who decides who is an expert?

It is for the court to decide whether the witness is suitably qualified. There is no technical or exhaustive list of what counts as an expert.


*Hopes and Lavery v HM Advocate 1960

⁃ Two were charged with extorting money by threats and the police had one of the victims wear a wire to record a conversation. In this case since the conversation was unclear the stenographer had made a transcript of what had been said. There were questions over the stenographer's expertise since she had no qualifications or experience in doing this. The court held that because she had no special qualifications or expertise, her evidence was of doubtful competency but ultimately looking at the particular circumstances the evidence had been correctly admitted.
⁃ [Thus the decision as to whether an expert witness is suitably qualified depends on the facts of the case.]
- So this turns on the circumstances of the case.


White v HMA 1986

**look up

Dealt with the question of how much of a drug a user would usually consume.


*Hainey v HM Advocate [2013]

⁃ Woman charged with murdering her baby son by wilfully ill-treating and neglecting him. At the trial the defence wanted to lead expert evidence that showed that the child's death could have been caused by either natural or unnatural causes and that if she had been chronically neglecting her son you would expect to see fractures in the bones (but none of these showed up in the post mortem). The Crown also tried to lead expert evidence from forensic anthropologists, neither of whom were medically qualified, to the effect that there were harris lines on the baby's bones which might indicate pre-death stress from neglect and malnutrition. The problem was that this theory about harris lines (lines of baby’s bones which can indicate pre-death stress from malnutrition) was seriously questioned in expert writing and the expert witnesses for the defence led evidence that harris lines can be seen in normal children too.
⁃ The trial judge gave the jury the advice that they should scrutinise this evidence and approach it with great care, but nevertheless the accused was convicted.
⁃ She appealed and the court held that the trial judge's failure to direct the jury that they should disregard this evidence amounted to a material misdirection so her conviction was overturned - the reason was that both of the forensic anthropologists accepted that they didn't have the necessary expertise to make these claims but the trial judge hadn't direct the jury that they should ignore this evidence.
⁃ The court also observed that questions as to the competence and experience of expert witnesses were for the trial judge to determine and that he or she has a continuing role throughout the proceedings to make sure they are conducted fairly. One of these roles the court must take on when making sure that the trial goes fairly is that when an expert is called upon to give evidence but clearly don't possess the knowledge that they'd be required to have to be classed as an expert, they (the judge) must tell the jury to disregard that evidence.


To what extent can an expert rely on published material (in the field in which they are an expert)?

Davie v Magistrates of Edinburgh 1953
⁃ A sewer was being constructed and a number of houses around the area were damaged and the owner's of these houses were trying to claim that the damage was caused by blasting operations. They led scientific evidence to the effect that the explosions were what caused the damage (but not expert opinion evidence)
⁃ The defender's led evidence from a number of experts. One said that the explosions couldn't have caused the damage. The second agreed. The third gave evidence that contradicted the first. The first expert was relying on a scientific pamphlet. The court held that it wasn't bound to accept the conclusions of experts. As regards the pamphlet the judge was only allowed to rely on the passages of the pamphlet insofar as the witness had adopted them himself or had been put to him in cross-examination.
- They defender tried to show that these blasts were not the result of the blasts. In doing so, they led three experts and witnesses to give their opinion on the matter. There were questions raised about the qualification of the second expert. The first expert that said they explosions could not have caused the damage tried to make reference to scientific pamphlet in support of their views. The court emphasised that the jury were not bound to accept the views of the expert witnesses. The court also said that the only passages from the published material that the court were allowed to rely upon were those which the expert had adopted for him/herself and had been cross-examined on. They could not refer to the entire pamphlet.


Main v McAndrew Wormald Ltd 1988

⁃ A man was exposed to asbestos during employment and died of lung cancer. The question was whether there was enough evidence to show that the cause of the cancer was his asbestos exposure. The court held that the expert witnesses were allowed to rely on medical literature given by epidemiologists.


Abadom (1982) 76 Cr App R 48



What is the presumption of foreign law?

Note the peculiarity that foreign law is a question of fact, and so expert evidence can be admitted on this point; but there is a rebuttable presumption that Scots law and foreign law are identical: see Emerald Stainless Steel v Southside Distribution Ltd 1982 SC 61.
So they will assume that foreign law is the same as Scots Law.


What is the rule about the factual basis for the expert's evidence?

The factual basis for the expert's evidence must be established in itself.


Forrester v HM Advocate 1952

⁃ The accused was suspected of safe blowing. An expert witness had given evidence about fibres found in the pocket of the accused. These fibres were really important because they were the only thing that connected the accused to the crime itself. But because the Crown didn't establish the source of these fibre,s it was held that the jury should not have been able to take into account the expert evidence. So the factual basis of where these fibres came from hadn't been established initially and this fact in itself meant that the expert evidence that related to these fibres should not have been heard by the jury.
⁃ [So in order to allow expert evidence to be admitted it must also be established that the facts on which they are basing their evidence have been established themselves.
⁃ NB the issue arising in this case is now dealt with by CPSA 1995 s 68): which says that the accused is allowed to see all productions (evidence) before his or her trial.


McD v HM Advocate 2002 SCCR 896.

Not lectured on.


What is the 'accuracy of the science concern'?

Is the field itself sufficiently well-established to be considered an area of expertise by itself, I.e. It must qualify as a science of discipline that the law is willing to give attention to.

These cases suggest that this is changing:
Hainey v HM Adv 2002; Young v HM Adv 2014:


Hainey v HM Adv 2002

Court also raised the issue here that whether the body of knowledge about harris lines was reliable enough in itself to be considered as a body of knowledge reliable in court.


Young v HM Adv 2014

Appeal against a murder conviction on a technique of “case-linkage” Expert witness was trying to argue that someone other than the appellant had actually killed the person the appellant had been convicted of killing — in a number of linked cases. Two witness: one spoke about the safety of the technique, the other witness talked about the weaknesses of the approach.

Held: this type of analysis was not sufficiently enough developed to possess the qualities required for proceedings. It should be based on a recognised and developed academic that proceeds on theories that have been tested. It should be found to have a practical and measurable consequence in real life. Follow a developed methodology that is open to challenge (6) produce a result capable of being assessed and giving more of less weight

[Look this case up***]