Alice punches Bob. Or stabs him. Either way it was from behind and he did not see who did it before going unconscious, but the entire thing was witnessed by Charles. However there was no other evidence of Alice’s crime like video footage or the like.

Charles testifies as to what he witnessed. Is Charles’s word enough to convict Alice of a crime?

What if it was also witnessed by Diana and they both testify, what then?


Or, Generally speaking, if someone presents to police and then court saying with a consistent narrative of events “this person hit me at the place and this time,” and there is perhaps a bruise to back it then that is often enough to convict the accused?

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    Did Alice have an alibi? Did the alibi check out? Did Alice have a motive? Did Alice take the stand and testify in her defense? What was her testimony? Did Charles and Diana know Alice before hand such that their identification of her could be considered credible? Or did they see the incident from a distance and pick her out of a lineup based on clothing? This is why we have juries… Jul 15, 2023 at 15:16
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    @MichaelHall what do juries have to do with any of this? If anything, that's why we have lawyers defending the accused.
    – DonQuiKong
    Jul 16, 2023 at 8:26
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    @DonQuiKong Despite their formalism, trials aren't a purely mechanistic process (e.g. "One eyewitness gives you 20 guilty points, and each additional independent witness adds another 10.") There's a lot of subjectivity and judgment calls involved. "This is why we have juries..." not to apply rigid formalism, but to perform this subjective fuzzy judgement call balancing act, incorporating potentially conflicting and sometimes misleading information, hopefully in a way that's consistent with prevailing societal expectations.
    – R.M.
    Jul 16, 2023 at 14:29
  • @DonQuiKong, R.M. Said it better than I might have, thanks. I will just add that yes, lawyers defending the accused is an important part of the process also. To ensure that the jury hears and considers all the issues, (and more…) that I brought up in my first comment before rendering a verdict. Jul 16, 2023 at 15:21

6 Answers 6


Is Charles’s word enough to convict Alice of a crime?

Usually yes unless his is discredited or found unreliable.

He may be discredited if he has history of being dishonest, especially if convicted for it.

He may be found unreliable if he is inconsistent about details of what he saw (e.g. tells different stories at different times), if he has had some conflicts with Alice, if he is on Bob's payroll and so on.

All those are just factors that the trier of fact may/will consider. There can't be an unequivocal yes or no.

  • If the question is about one person's word by itself: Someone can be perfectly honest otherwise, but they have enough of a grudge against the accused to fabricate a story. Or they may have been too quick to jump to a conclusion, and that ended up with them stuck in a web of lies. Or they may have just misremembered. Eyewitness testimony is unreliable. If there is no corroborating evidence, how can the answer be "usually yes"?
    – NotThatGuy
    Jul 17, 2023 at 10:42
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    @NotThatGuy That's what cross-examination is for — to surface all possible grudges, conclusion jumping, misremembering etc. If they surface, the "unless" condition triggers.
    – Greendrake
    Jul 17, 2023 at 11:07
  • You could sometimes establish witness unreliability through cross-examination, but it doesn't seem like that would work well enough to justify throwing someone in prison based on what one person said.
    – NotThatGuy
    Jul 17, 2023 at 11:21
  • @NotThatGuy Well, that's how it works, in adversarial justice systems at least.
    – Greendrake
    Jul 17, 2023 at 11:28

One might be enough, 10,000 might not be enough

In some cases, no eyewitnesses may be enough.

The trier of fact (the jury if there is one, the judge if there isn’t) decides what weight to give to the evidence or any part of it (including the testimony of any given eyewitness) and decide if that is enough to meet the prosecution’s burden of beyond reasonable doubt on each of the elements to be proven.

From the outset, however, you should understand that you are the sole judges of the facts. In respect of all disputes about matters of fact in this case, it will be you and not I who will have to resolve them. In part, that means that it is entirely up to you to decide what evidence is to be accepted and what evidence is to be rejected. For that reason you need to pay careful attention to each witness as their evidence is given. You should not only listen to what the witnesses say but also watch them as they give their evidence. How a witness presents to you and how he or she responds to questioning, especially in cross-examination, may assist you in deciding whether or not you accept what that witness was saying as truthful and reliable. You are entitled to accept part of what a witness says and reject other parts of the evidence.

Recommended instruction to the jury from the NSW Criminal Trial Bench Book


The number of witnesses does not mathematically add up to reasonable doubt or not. It all depends on what the jury finds credible. Dozens of witnesses who hated Alice would not be so credible as one witness who hated David, another suspect, and loved Alice but said that Alice had done it.

This is because what is required is to convince the jury. Toronto Defense Lawyers explains it:

The judge/jury does not need to be “absolutely certain” that the defendant is guilty to satisfy the standard of proof beyond a reasonable doubt. The prosecution need not prove guilt beyond any doubt whatsoever. Moreover, the judge/jury cannot acquit based on an imaginary or frivolous doubt.

However, the reasonable doubt standard requires more than simply that the jury be convinced that the defendant “probably” committed the crime or “likely” committed the crime.

Just as you would probably believe some things on few witnesses and disbelieve others with more witnesses because you find them less credible, so too with the jurors.


How many witnesses’ testimony constitute or transcend reasonable doubt?

Reasonable doubt is assessed based on the totality of the evidence (R. v. McClure, 2001 SCC 14, para. 60). There is no formula. See R. v. Lifchus, [1997] 3 SCR 320, para. 36:

  • the standard of proof beyond a reasonable doubt is inextricably intertwined with that principle fundamental to all criminal trials, the presumption of innocence;
  • the burden of proof rests on the prosecution throughout the trial and never shifts to the accused;
  • a reasonable doubt is not a doubt based upon sympathy or prejudice;
  • rather, it is based upon reason and common sense;
  • it is logically connected to the evidence or absence of evidence;
  • it does not involve proof to an absolute certainty; it is not proof beyond any doubt nor is it an imaginary or frivolous doubt; and
  • more is required than proof that the accused is probably guilty ‑‑ a jury which concludes only that the accused is probably guilty must acquit.

As part of that analysis, it is up to the trier of fact (judge or jury, depending on the trial) to assess each witness's credibility.

  • This was satisfyingly educational but sadly does not engage that much or properly address the question. Jul 14, 2023 at 23:48
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    Because there isn't an answer. The jury in each individual case decides. Like if a car salesman pitches a used car as being really nice and asking "is that often enough to convince them to buy the car?" The answer is sometimes yes, sometimes no. Jul 15, 2023 at 3:26

You would need some things to add up for “guilty beyond reasonable doubt”.

First, did the police see Bob lying on the ground, stabbed in the back, in a way that he couldn’t do himself and that couldn’t be an accident? Without an injured Bob, there is reasonable doubt that a crime happened at all.

Could Charles by mistaken? If Alice is one of 100 customers to enter Bobs store that day, then it could easily be a person who looks similar to Alice. If Bob, Alice and Charles have been coworkers for years, it is most likely no mistake. Unless Alice has an identical twin.

Could Charles be lying? With your story, I’d have the very reasonable doubt that Charles might be the attacker, and trying to put the blame on Alice. So your facts wouldn’t be enough.

Now another witness who saw what happened from a distance and could see it was a person with long hair like Alice and not a bald person like Charles, even though they can’t identify Alice, that would make a difference.

In the end a jury decides. It is not necessary that there is no other possibility than Alice being the attacker, but just finding it likely or highly probable that she is the attacker is not enough.

  • Doctors can probably certify that a back wound could not be self inflicted
    – Mary
    Jul 15, 2023 at 16:44

0 direct witnesses can be enough

It is upon the trier of fact to evaluate what happened. A case can be held entirely based on evidence with 0 witnesses that actually saw the act to establish guilt beyond a reasonable doubt. However, all those analysts and investigators, and other experts are to be called to explain the evidence and their significance... as witnesses. Not calling them as (indirect) witnesses means, the evidence should not come in under Melendez-Diaz v. Massachusetts, 557 U.S. 305 (2009).

Any number of witnesses - be they experts, investigators or direct eyewitness - that can make the finder of fact believe that it is beyond a reasonable doubt is enough. Any number can be 0 eyewitnesses, 0 experts, and the one 1 investigator saying "I met Alice an hour after the incident and she was acting strange when I told her Bob is dead."

A million people agreeing (based on hearsay) might not be

Since you need to convince the finder of fact that someone is guilty beyond a reasonable doubt, you could have millions of people that all claim Alice did it, maybe because of the news reports, but because nobody of them has more information than the news reporter, who invented half his story, all of their testimony is hearsay and worth nothing. They can not testify. Not even the investigator can testify about things told to them, as established by Crawford v. Washington, 541 U.S. 36 (2004), overruling Ohio v. Roberts, 448 U.S. 56 (1980).

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    If someone has no non-hearsay statements to make, then they aren't a witness. Jul 16, 2023 at 6:20

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