The trial judge, when explaining what is required of the jury, will direct them that a unanimous decision is needed.

Criminal Courts Blockbusters Quiz

There are 12 jurors and this means that all of them must agree on the verdict.  Time will be allowed for the jury to reach a verdict.  In the event that the jury fail to agree and are unable to reach a 'unanimous' verdict, the trial judge will give further guidance and may well direct that the court will accept a 'majority' decision i.e. this is normally 11:1 or 10:2.

The trial judge will mention the basis upon which they should decide the case.  The responsibility for making out the case against the defendant is upon the prosecution.

The jury must be satisfied beyond all reasonable doubt that the accused is guilty before they can reach such a verdict.  The modern equivalent is that they must be ‘sure’ that the accused did what he or she is accused of.