---
title: "What is the difference between \"under the influence\" and \"controlled substance present in blood\"?"
description: "\"Under the influence\" requires proof that marijuana actually impaired your ability to drive. \"Controlled substance present in blood\" only requires a positive test for THC, regardless of impairment...."
url: https://duiattorneyrhodeisland.com/faq-items/what-is-the-difference-between-under-the-influence-and-controlled-substance-present-in-blood/
date: 2026-06-19
modified: 2026-06-19
author: "Criminal Defense Attorney Rory Munns"
type: faq
lang: en
---

# What is the difference between "under the influence" and "controlled substance present in blood"?

"Under the influence" requires proof that marijuana actually impaired your ability to drive. "Controlled substance present in blood" only requires a positive test for THC, regardless of impairment. The penalties for the "present in blood" charge are lighter, but both can result in a DUI conviction and license suspension. Rory often defends both charges at once and shapes the strategy around the difference in proof burdens.