Witness statements do not have to harmonize exactly, but if there are discrepancies in the main points, sit down with each witness to find out why that difference exists. There are various reasons why there may be discrepancies:
Someone may not have been present at all times.
The witness may have been present only at the start or the finish of the event.
The witness may not have been able to hear all that transpired over surrounding noise.
The statements should be amended, if necessary, by the witnesses themselves to account for these differences. This can be done in a separate document or by an attachment to the original statement. If any differences cannot be reconciled, then those differences demand investigation ...