The short answer is ‘All relevant evidence that a witness can give.’
For the long answer, keep reading.
A witness statement should be complete. You cannot rely on a tribunal’s indulgence to expand on what you’ve said or to ask follow up questions of the witness. Even if they do let you do this, it is better to put the information in to begin with. It will be one less thing to worry about, and you can present it in an organised, thought-out manner.
The exception to this is when new issues are raised by the other-side in their witness statements.
Occasionally, this will be something sufficiently significant or involved that it is sensible to put in a supplementary statement. But often, a quick question in examination in chief is better. The form is usually something like “In his witness statement, Mr Smith says that the company handbook was available on the staff notice board. What do you say about that?”
Such questions should be asked sparingly, when you have something to add to the original evidence. Is it not necessary to go through all the the otherside’s statements, saying where they are wrong. If, for example, your witness says in her statement statement that she agreed to work for £100 per day, it is pointless to ask “Mr Jones says in his statement you agreed to work for £50 per day. What do you say to that?” The answer is obvious.
A witness statement should include everything relevant, and nothing irrelevant.
This is much easier to say than to do. The starting point is to have a clear list of issues that the tribunal will need to decide. Then put in all the evidence that will help them do so.
There is no rule about how long a statement should be. It will vary from case to case and witness to witness. However, it will normally be proportinate to the length of the hearing. If you have a 30 page claimant’s statement for a 2 hour hearing, it is a sign that something is wrong. Similarly, if you have a 3 page claimant’s statement for in a 10 day discrimination case, the chances are that it does not go into enough detail. Bear in mind that this is general guidance and there are always exceptions.
The witness statement is for evidence, rather than submissions. It should tell the tribunal what has happened, rather than tell them what to think about it. The latter is something for submissions.
Having said that, a witness statement should be organised in a way that makes is easy for a tribunal to understand what it is you will be saying. If, after all the evidence is in and you are about to start making submissions, the tribunal has no idea what you will be saying, something has gone badly wrong.
‘That a witness can give’
Occasionally you will see a witness statement that sets out the evidence of other people as well as the witness giving it. For example, it may say something like ‘Ms Smythe, the HR Manager, will say that …’ This is pointless. Ms Smythe should have her own witness statement setting out what she is going to say.
It is important not to confuse this point with the issue of ‘hearsay evidence’. Hearsay is a rule of evidence from the criminal and civil courts. The precise definition is complex, but in broad terms it is evidence from a witness about what somebody else has told them.
For example, if Mr Sampson gives evidence that Ms Brook told him that Mr Jones told her that ‘nobody sensible would appoint a woman who might get pregnant’ then Mr Sampson is giving hearsay evidence. He is one step removed from the incident and can only tell the tribunal what Ms Brook told him.
Hearsay evidence is permitted in the tribunal and is quite common. It is, however, normally better to have direct evidence. If, in the above example, it was possible to call Ms Brook, that is more likely to convince the tribunal. Of course, by the time you get to tribunal Ms Brook may have regretted her candour and refuse to assist.