Let me rephrase that....?

my friend was arrested for 11550 - under the influence - when the work location he was at was raided by Narcs. He had no drugs on him. none were in the house. his client (owner of the home) had drugs on him (personal use) and he was caught outside in his parking garage. They took him in after finding probable cause due to a rapid pulse. SWAT had just broken down the door and my friend was working in the home alone (client was out getting food). of course he will have a rapid pulse. the 4th ammendment says that a misdemeanor charge must be commited in the presence of the arresting officer but a felony only requires probable cause for an arrest. My friends charge is misdemeanor. Does the proscecutor have a strong case against my friend?