“The autopsy found no evidence that he had drugs within the 72 hours before the incident,”
This makes no sense at all. It suggests 3 days prior he had his bloods analysed. At his autopsy a blood sample would be taken and sent for toxicology for analysis; this test takes 4-6 weeks. I'm suggesting they did a rapid antigen test by saliva or air squeezed from bronchus and obtained a NEG reading, mimicking the reading obtained from a road-side breath testing device.