Challenging the accuracy of a breath or blood test often involves reviewing maintenance, calibration, and operator records for testing equipment, as well as the chain of custody for samples. Defense may question whether the device was functioning properly, whether testing procedures were followed, or whether medical conditions or recent consumption could have affected results. Technical review by appropriate reviewers can uncover weaknesses in testing protocols that affect admissibility or weight of evidence. Additionally, errors in how tests were administered at the scene or station, or delays in obtaining samples, can be relevant defenses. Counsel can request laboratory records, inspect documentation, and present arguments that test results should be excluded or given less weight based on procedural shortcomings or scientific concerns.