In State V

In State v. Gonzalez, a police officer made a traffic stop of a woman who had been speeding, and after that smelled the odor of marijuana coming from inside the car. The officer noted some of the effects of marijuana appeared to be observable in the defendant, and at trial he testified that she was under the influence of marijuana and was incapable of safe driving at the time she was operating the motor vehicle. Although the trial court allowed the officer to explain why he believed the driver, Gonzales, was under the influence of marijuana, the officer's testimony was not supported by substantial evidence. The officer testified that red eyes and body tremors were symptoms shared between marijuana and alcohol, but he did not administer a breath test for alcohol to defendant Gonzalez. A blood test for alcohol was performed, but was never introduced in evidence. Why did the appellate court reverse the defendant's conviction for driving under the influence of a drug when the police officer testified concerning his observations? Explain.