The public safety exception does not set a hard time when questioning must stop and the suspect must be taken into court, but it's generally understood to be about 48 hours.
Scientists don't usually test for cyanide in the battery of toxicology tests they may run in a suspicious death and don't generally look for it unless there is a reason to suspect it.
We found Mr. Vandegrift to be generally honest and forthright, but his time estimate is suspect given his employment as a salesman for an employer in a business unrelated to the real estate activity.