“They may not be necessary, but they may make the difference in that case from proving liability. In other words, if there are 10 eyewitnesses that say the truck rear-ended the car, you may not need an expert in that case. But if you’ve got jackknifing, over-steering, over-braking, any of the other type of truck/auto cases, you may need an expert to prove that type of liability against the trucking company.”