After the exhumation and examination of William's body by multiple doctors and chemists, it was determined that he had, indeed, been poisoned by arsenic. The questions that now concerned the police were: How? and By whom?
It had been discovered that Lino had purchased several ounces of the powder from Mr. Durand's drug store in Philadelphia the day prior to the onset of William's symptoms. He also allegedly had three vials of arsenical waters in his trunk when he was arrested in Boston. This appeared to answer the first question, at least in regard to how the poison was obtained. Lino had stated that he was making a collection of birds, and that he wished the arsenic for the purpose of using it in their preparation. No evidence was ever found that he had been engaged in collecting birds.
So the poison was in the house. Did Lucretia know about or authorize the purchase? Were Lino and her both involved in a conspiracy to kill William? How exactly did William come to ingest the poison?
On Monday, 20 July, the Chapmans' neighbor, Benjamin Boutcher, was mowing in his lot when he saw a chicken come from his neighbors' yard, which was about 60 or 70 yards away from his home. It was coming across the road and it died before it got across. There were three chickens that died that likewise came across the road from the Chapmans' yard. He did not think much of it at the time.
The next day, however, a significant number of ducks owned by Benjamin died in a very sudden, and at the time, in a very unaccountable way. The ducks, like the chickens from the day before, had been in the habit of going to the Chapmans. On that day, between two and three o'clock, Benjamin looked over towards his neighbor's property as he was going to his shop. The ducks were on their way home, coming in a row, one after the other. Benjamin thought they seemed to be worried. He had a fair sight of them and then he saw Lino standing by a buttonwood tree. The ducks came beyond where he stood, about ten yards. Before the ducks came through into the road, one of them fell over, dead. The rest came through the fence where the waste water emptied, and then another fell over. When they got nearly across the road, another fell over. One of Benjamin's sons came out and was told to take care of the ducks and he went into his shop.
After a little while, his son came and said that another one was dead, and he thought they would all die. Benjamin told him to bury them. There were between twenty and thirty that died that day and the next. Four of the ducks could not get through into the Chapmans' yard; those did not die. Benjamin told his wife he thought they had been poisoned. Previously, they had only raised chickens and had never kept ducks, but he did not believe it was a common thing for them to just fall over and die.
Lucretia had, in fact, purchased a chicken from the Boutchers and used it to make soup for William on Monday.
Of all the Boutchers' poultry, chickens and ducks, only those should die which had been feeding within the premises of the deceased. It was concluded that they were infected by the presence of a poisonous material, and that too on the day when poison was proven to be in circulation at the Chapmans'.
During the trip from Boston back to Philadelphia, Constable Blayney had multiple conversations with Lino. After he had asked Lino if he had given William any of the medicine and Lino replied no, that he was innocent, Lino let slip a detail, whether intentional or not. He said that when the woman brought up the bowl of soup, Lucretia took the soup from the woman and she then put the "physic" in the soup. "Did you see the physic?" Blayney asked him. Lino said, "No-she take it from my bottles. After Mr. Chapman take the soup, he get very bad and die." This was the first mention Blayney had ever heard about the soup.
Ann Bantom said Lucretia made the soup, put a little salt in it in the kitchen, and told her she would take it to the parlor and season it. Ann left her in the parlor but returned to get something she had forgotten. There she found only Lino and Lucretia in the room. Lucretia carried the soup up to William. He ate some of the soup and a far amount of the chicken, leaving the neck, wing and part of the back. Immediately after taking the soup, William grew worse and complained of a burning heat in the stomach. The remainder of the soup and the chicken were thrown into the yard by Ann , thus making it available for the fowl to consume.
Investigators concluded that it must have been the chicken soup that had been "seasoned" with arsenic. Both Lino and Lucretia were responsible for the deed and would be tried for the murder of William Chapman. Lucretia still was still on the run and had to be found and brought back for a trial to occur. Lino was already in custody...at least for now.