The first of our favorite things to do in Dallas Texas is a visit to the Dallas Aquarium (aka Dallas World Aquarium), which is a fascinating place.
In the United States and other countries, evidence may be excluded from a trial if it is the result of illegal activity by law enforcement, such as a search conducted without a warrant. Such illegal evidence is known as the fruit of the poisonous tree and is normally not permitted at trial.
The testimony of A, B, C, and D constitute a chain of custody for the drugs, and the prosecution would need to offer testimony by each person in the chain to establish both the condition and identification of the evidence, unless the defendant stipulated as to the chain of custody in order to save time.