Last month, I observed a case at Wood Green Crown Court, where a witness to a GBH was awarded £400 by a judge for her "public-minded spirit".
The witness saw a cyclist dragged from his bike by his rucksack and then stamped on, resulting in a broken sternum and other injuries. The attacker was a car driver who'd had an earlier altercation with the cyclist. The witness took a photo of the registration number of the car and with this information, the police could identify the attacker. The witness also went one step further, and with less than a day's notice, attended court to give evidence. On the day of trial, the defendant pleaded guilty.
Legal guidance on witness awards
Section 28 of the Criminal Law Act 1826 provides that where a person appears to the Crown Court to have been active in or towards the apprehension of any person charged with an indictable offence, the Crown Court may order a sum of money that the court deems reasonable and sufficient to compensate such a person.
There is little other guidance on these awards. The CPS guidance on judicial comments simply states that the court will sometimes publicly commend a witness and/or financially reward a witness. Normally, no more action will be required than a note on the file.
The Court of Appeal has considered witness awards in criminal proceedings twice, on both occasions finding that witness awards should not be given in the presence of the jury, unless at sentencing.
In R v Spiteri  Crim LR 419, the sole prosecution witness was awarded a sum by the judge during evidence. The judge stated that the witness ought to be thanked for reporting what she did. In summing up, the judge reminded the jury to pay no attention to the fact he had made an award to the witness. The defendant was convicted. The appeal was successful. It was held that it was not appropriate to award a witness during a trial.
In R v Haigh  Crim LR 263, a witness was awarded £25 in the jury's presence for alerting the police of a burglary. The Court of Appeal held that the £25 award was so prejudicial that the conviction should be quashed.
Other examples of witness awards
Witness awards are relatively rare. I have only been able to find two other recent examples:
October 2013 - Key witness in murder trial awarded £1000 by judge (Evening Standard)
April 2009 - Witnesses commended and given financial awards (Nottingham Post)
Although the awards may be rare, witnesses are also entitled to claim expenses. The CPS is responsible for paying allowances and expenses to witnesses who are called to give evidence in prosecutions conducted by the Service. Witnesses may receive compensation for travelling expenses, money spent on refreshment meals, financial loss (e.g. loss of earnings) and other expenses incurred (e.g. childcare). More information can be found on the CPS website here.