What evidence type is most effective in supporting a DUI conviction?

Reliable and legally obtained chemical test results are considered the most effective type of evidence in supporting a DUI conviction. This is because chemical tests, such as breath, blood, or urine tests, provide objective and quantifiable measurements of a driver's blood alcohol concentration (BAC) or the presence of drugs. These tests are typically administered following strict protocols to ensure their legality and accuracy, making the results credible and admissible in court.

In DUI cases, the legal limit for BAC is set at 0.08% in many jurisdictions, and having a chemical test result that exceeds this limit serves as strong evidence of impairment. The scientific backing of these tests enables them to be upheld in court, as they rely on standardized methods that are generally accepted within the criminal justice system.

While witness statements, personal experiences of the officer, and surveillance footage can contribute context or additional evidence in a case, they do not provide the same level of objective, quantifiable proof of impairment that reliable chemical test results do. Such evidence may be subjective or open to interpretation, which can weaken its impact in securing a conviction.