If you are a witness in a criminal trial in Florida, you typically testify as to what you observed (facts). (the light was green, the suspect wore a red shirt and bluejeans)
Generally, opinion testimony is limited to people qualified as “experts” in a particular field. For example, a doctor can testify as an expert and give his or her opinion on medical matters. The expert must have scientific, technical, or another specialized knowledge that will help the jury to understand evidence or to determine a fact in issue.
If a lay person can only give their opinion if the opinion doesn’t require special knowledge, skill, experience, or training. Their opinion must also not mislead the jury. They can testify as to someone’s physical appearance, such as the person looked “angry” or “fearful”.