The two Knapps were young shipmasters, of a respectable family.

Joseph J. Knapp, Jr., on the third day of his imprisonment, made a full confession that he projected the murder. He knew that Mr. White had made his will, and given to Mrs. Beckford a legacy of fifteen thousand dollars; but if he died without leaving a will, he expected she would inherit nearly two hundred thousand dollars. In February he made known to his brother his desire to make way with Mr. White, intending first to abstract and destroy the will. Frank agreed to employ an assassin, and negotiated with R. Crowninshield, Jr., who agreed to do the deed for a reward of one thousand dollars; Joseph agreed to pay that sum, and, as he had access to the house at his pleasure, he was to unbar and unfasten the back window, so that Crowninshield might gain easy entrance. Four days before the murder, while they were deliberating on the mode of compassing it, he went into Mr. White's chamber, and, finding the key in the iron chest, unlocked it, took the will, put it in his chaise-box, covered it with hay, carried it to Wenham, kept it till after the murder, and then burned it. After securing the will, he gave notice to Crowninshield that all was ready. In the evening of that day he had a meeting with Crowninshield at the centre of the common, who showed him a bludgeon and dagger, with which the murder was to be committed. Knapp asked him if he meant to do it that night; Crowninshield said he thought not, he did not feel like it; Knapp then went to Wenham. Knapp ascertained on Sunday, the 4th of April, that Mr. White had gone to take tea with a relative in Chestnut Street. Crowninshield intended to dirk him on his way home in the evening, but Mr. White returned before dark. It was next arranged for the night of the 6th, and Knapp was on some pretext to prevail on Mrs. Beckford to visit her daughters at Wenham, and to spend the night there. He said that, all preparations being thus complete, Crowninshield and Frank met about ten o'clock in the evening of the 6th, in Brown Street, which passes the rear of the garden of Mr. White, and stood some time in a spot from which they could observe the movements in the house, and perceive when Mr. White and his two servants retired to bed. Crowninshield requested Frank to go home; he did so, but soon returned to the same spot. Crowninshield, in the mean time, had started and passed round through Newbury Street and Essex Street to the front of the house, entered the postern gate, passed to the rear of the house, placed a plank against the house, climbed to the window, opened it, entered the house alone, passed up the staircase, opened the door of the sleeping-chamber, approached the bedside, gave Mr. White a heavy and mortal blow on the head with a bludgeon, and then with a dirk gave him many stabs in his body. Crowninshield said, that, after he had "done for the old man," he put his fingers on his pulse to make certain he was dead. He then retired from the house, hurried back through Brown Street, where he met Frank, waiting to learn the event. Crowninshield ran down Howard Street, a solitary place, and hid the club under the steps of a meeting-house. He then went home to Danvers.

Joseph confessed further that the account of the Wenham robbery, on the 27th of April, was a sheer fabrication. After the murder Crowninshield went to Wenham in company with Frank to call for the one thousand dollars. He was not able to pay the whole, but gave him one hundred five-franc pieces. Crowninshield related to him the particulars of the murder, told him where the club was hid, and said he was sorry Joseph had not got the right will, for if he had known there was another, he would have got it. Joseph sent Frank afterwards to find and destroy the club, but he said he could not find it. When Joseph made the confession, he told the place where the club was concealed, and it was there found; it was heavy, made of hickory, twenty-two and a half inches long, of a smooth surface and large oval head, loaded with lead, and of a form adapted to give a mortal blow on the skull without breaking the skin; the handle was suited for a firm grasp. Crowninshield said he turned it in a lathe. Joseph admitted he wrote the two anonymous letters.

Crowninshield had hitherto maintained a stoical composure of feeling; but when he was informed of Knapp's arrest, his knees smote beneath him, the sweat started out on his stern and pallid face, and he subsided upon his bunk.

Palmer was brought to Salem in irons on the 3d of June, and committed to prison. Crowninshield saw him taken from the carriage. He was put in the cell directly under that in which Crowninshield was kept. Several members of the Committee entered Palmer's cell to talk with him; while they were talking, they heard a loud whistle, and, on looking up, saw that Crowninshield had picked away the mortar from the crevice between the blocks of the granite floor of his cell. After the loud whistle, he cried out, "Palmer! Palmer!" and soon let down a string, to which were tied a pencil and a slip of paper. Two lines of poetry were written on the paper, in order that, if Palmer was really there, he should make it known by capping the verses. Palmer shrunk away into a corner, and was soon transferred to another cell. He seemed to stand in awe of Crowninshield.

On the 12th of June a quantity of stolen goods was found concealed in the barn of Crowninshield, in consequence of information from Palmer.

Crowninshield, thus finding the proofs of his guilt and depravity thicken, on the 15th of June committed suicide by hanging himself to the bars of his cell with a handkerchief. He left letters to his father and brother, expressing in general terms the viciousness of his life, and his hopelessness of escape from punishment. When his associates in guilt heard his fate, they said it was not unexpected by them, for they had often heard him say he would never live to submit to an ignominious punishment.

A special term of the Supreme Court was held at Salem on the 20th of July, for the trial of the prisoners charged with the murder; it continued in session till the 20th of August, with a few days' intermission. An indictment for the murder was found against John Francis Knapp, as principal, and Joseph J. Knapp, Jr. and George Crowninshield, as accessories. Selman and Chase were discharged by the Attorney-General.

The principal, John Francis Knapp, was first put on trial. As the law then stood, an accessory in a murder could not be tried until a principal had been convicted. He was defended by Messrs. Franklin Dexter and William H. Gardiner, advocates of high reputation for ability and eloquence; the trial was long and arduous, and the witnesses numerous. His brother Joseph, who had made a full confession, on the government's promise of impunity if he would in good faith testify the truth, was brought into court, called to the stand as a witness, but declined to testify. To convict the prisoner, it was necessary for the government to prove that he was present, actually or constructively, as an aider or abettor in the murder. The evidence was strong that there was a conspiracy to commit the murder, that the prisoner was one of the conspirators, that at the time of the murder he was in Brown Street at the rear of Mr. White's garden, and the jury were satisfied that he was in that place to aid and abet in the murder, ready to afford assistance, if necessary. He was convicted.

Joseph J. Knapp, Jr. was afterwards tried as an accessory before the fact, and convicted.