What is a DRE?

A DRE stands for a drug recognition expert, it's essentially an officer that has had some type of extending training in identifying a person under the influence of a controlled substance or drugs. Now most of the times, officers are not DRE's and therefore when they give you the HGN test or the horizontal gaze nystagmus test it's not admissible in the court. However courts have ruled that if that officer is a DRE that the horizontal gaze nystagmus test is admissible.