The poison in the drink jar in the garden that the bride took by mistake was poisoned by the bride after taking it by mistake. After the groom puts the poison and the semi-melted capsule into the drink at the same time, he will think that the poison in the capsule has melted, so it has been put for some time. The melting time of capsules is calculated by computer, and the poisoning time is inferred, which makes people think that the groom has not touched the drink when poisoning. Besides, regarding fingerprints, the bride took the wrong drink can. After the bride's father came into contact with another student's drink, because there were no fingerprints of these two people on the toxic drink, it was inferred that the poisoning was after the bride took the wrong jar, and only the groom touched the jar during this time, so the murderer was the groom.