New research says child witnesses face incomprehensible language and much distress at court.
The study by Auckland University of Technology also shows it now takes an average of 15 months for a case to be heard, double the time it used to take in the 1990s.
Co-author Emma Davies says the process needs to be quicker and easier for those under 17 years of age.
Dr Davies says improving the current system will encourage children to give the best evidence, which is in the interest of the courts.
She suggests that courts consider alternative methods such as pre-recorded cross and re-examination by a court appointed specialist.