These are witnesses who assist the court in areas of expertise such as medical reports, ballistic reports, handwriting experts, government analysts – its not in all cases that expert witnesses are necessary it is only in some cases i.e. where a firearm is used a ballistic expert, handwriting a handwriting expert.
The general rule of practice is that expert witnesses should be given priority over other witnesses. This is the practice irrespective of whether he is the next witness to be called logically
The evidence of such witnesses may be challenged by other experts. One can be challenged by another expert. It is not common in Kenya as we have not developed the norm of people challenging expert evidence. For example in rape and defilement a medical report is required which indicates about blood and semen tests but in developed countries they require DNA testing.