What does it take for witness testimony to be believed?
<p>I'm imagining a very generic situation of violence. Say there are two groups of people, W (witnesses) and A (accused). Some members of group A are accused of an act of violence from all members of group W. All members of group A, whether directly accused or not, deny this accusation.</p>

<p>Apart from this witness testimony, the only other piece of evidence are the injuries sustained by members of group W. However, these injuries are minor enough so that they could be self-inflicted (e.g., torn clothes, a few bruises, or a small flesh-wound cut from a knife). </p>

<p>There is no other evidence. No physical evidence, like a knife or a security camera. Nobody has an alibi either. And there's no good reason for <em>why</em> the supposed violence occurred. The members of W simply claim that it happened and that it was perpetrated by members of A. </p>

<p>The situation is generic, but I think I have described it well enough for one to address it specifically. What happens? With whom does the Law side? How does the answer depend on the sizes of group W and group A? </p>

<h2>Common Law</h2>

<p><strong>The trier of fact decides the credibility of witnesses</strong></p>

<p>The trier of fact for a criminal matter is usually a jury. They decide what witnesses to believe and how much they believe them. </p>

<p>Common law uses an adversarial approach - the court is not (particularly) interested in determining the truth, the role of the court is to decide the dispute between the parties. If the parties agree the sky is green, it is not for the court to find that it is blue.</p>

<p>Each witness has a direct examination, and is then available for cross-examination by the other side and potentially redirect examination by their side (a witness is always a prosecution or a defence witness). There may or may not be physical or documentary evidence introduced by one (or more) witnesses and the testimony of those witnesses determines how much that is worth (e.g. there is never just a pathologist’s report - it is always supported by the testimony of the pathologist(s)).</p>

<p>The jury is free to believe some, none or all of any given witnesses testimony for whatever reason they choose. They then decide if the evidence they believe satisfies the prosecution’s burden of proof beyond reasonable doubt - if so, the verdict is guilty, if not, its not guilty.</p>

<p>For a bench trial the judge is the trier of fact as well as law. They do the same thing except that they have to publish their reasons, jury’s don’t. </p>

<h2>Civil Law</h2>

<p>There are generally no juries in civil law jurisdictions so this all falls on the judge(s). However, civil law courts are much more inquisitorial rather than adversarial - their role is to determine the truth independently of what each side is arguing.</p>

<p>This means the judge has more leeway in probing witnesses and pursuing their own lines of inquiry - a judge that does that too much in a common law court is going to get rolled on appeal.</p>

<p>Notwithstanding, they still decide whether they believe the witness or not so it comes down to pretty much the same thing.</p>

<p>The jury or the judge, depending, has to make up their mind which testimony they believe the most.</p>

<p>The number of people in each group is not very relevant.  There are cases where "everybody" agrees that a scapegoat is guilty, and there are other cases where a large number of criminals give each other alibis.</p>

<p>In jurisdictions where "innocent until proven guilty" is a rule, the defender will make a point of how unreliable witness statements are. Maybe the alleged victim has a grudge against the alleged perpetrator. Maybe the rest of the W group are friends of the the alleged victim and will support anything they say.  The defender will do anything to raise a "reasonable doubt" and argue that this mean acquittal.</p>

<p>What is most important for someone considering a witness statement is <strong>consistency</strong>.</p>

<p>The defender will try to find inconsistencies in the statements of group W, while the prosecutor will try to do the same for group A.  Any inconsistency, no matter how small, will be used to discredit the whole statement.</p>

<p>There are several types of inconsistencies.  First there is if a single witness contradicts themself on the witness stand.  Second is if a witness changes explanations from the first police interviews to later.  Third is two different witnesses from the same group contradict each other.  This will throw both statements in doubt.</p>

<p>This is the source of most courtroom drama, either lawyer pushing the witnesses until they can't keep their (alleged) lies straight.</p>

<p>After both sides has done their best to discredit the other, it is up to the jury or the judge to decide which story is most believable.  It can be a very difficult job.</p>

witnesses