The Trial and the Fingerprint Evidence

Step three: he explains the science before he uses it. He tells the court that every human being carries from cradle to grave physical marks which do not change, by which he can always be identified without shade of doubt. They are, he says, a man's "physiological autograph", which cannot be counterfeited, disguised, hidden or worn away. Not the face, which age changes; not the hair, which falls out; not the height or the form, of which duplicates exist.

Step four: he makes the evidence visible. He has enlarged his glass-plate records ten times with a pantograph onto white cardboard and reinforced every line with ink, so that patterns which look alike to the naked eye can be told apart at a distance of many feet.

Step five: he lets the jury do the comparing. He hands the foreman a powerful magnifying glass. The jury compare the accused men's prints with the marks on the window panes, and report that they are identical. They compare the same cardboard with the signature on the knife handle, and report that they are exactly identical. Then he asks them to compare the prints of the accused with the prints left by the assassin, and the foreman answers: "They do not even resemble."

Step six: he turns from acquittal to accusation. "These men are innocent. I have no further concern with them. We will now proceed to find the guilty."

Step seven: the infant records. He produces the finger-prints of two children, called A and B, taken at five months and again at seven months. Each child's two sets tally. Then he produces prints of each at eight months, and neither tallies with that child's earlier ones. He gives the jury the explanation: somebody changed those children in the cradle, between seven months and eight months, and the person who did it is in this house.

Step eight: the identification. He produces A's print at the age of twelve, and asks the jury to compare it with the assassin's signature on the knife handle. The foreman answers: "To the minutest detail!" Wilson then names him.

The murderer of your friend and mine, York Driscoll of the generous hand and the kindly spirit, sits in among you. Valet de Chambre, negro and slave, falsely called Thomas à Becket Driscoll, make upon the window the finger-prints that will hang you!

Tom slides to the floor in a faint. Wilson's last words in the scene are "There is no need. He has confessed."

What is proved, and what is only guessed

An examiner will reward a candidate who separates them.

Proved by the records. That the marks on the knife are not the twins'. That the marks on the knife are the accused Tom's. That the two children were exchanged between seven and eight months. All three rest on the same physical evidence and are checked by the jury themselves.

Guessed, and admitted by Twain to be guessed. The motive of robbery. The person in the room beforehand. The man in woman's clothes at the back gate. Twain says explicitly that Wilson tried "a few hardy guesses" which could help if they hit and would probably do no harm if they missed.

The point worth making in an essay. Wilson wins by combining certainty with bluff, and Twain tells the reader which is which. That honesty is what makes the chapter a study of advocacy and not just a conjuring trick.

Would a court in 1830 have accepted it?

This is the best question that can be asked about the chapter, and the honest answer has three parts.

No court did. Fingerprint identification was developed as a system in the later nineteenth century, decades after 1830 and only shortly before Twain wrote in 1894. The novel is deliberately anachronistic.

The demonstration is designed to answer that objection. Notice that Wilson never asks the court to take the science on trust. He explains the principle, enlarges the marks so that they can be seen from across the room, and then has the jury perform every comparison themselves with a magnifying glass. It is proof by demonstration rather than by expert opinion, which is exactly how a court with no rule on the subject could have been persuaded.

And Twain knows what he is doing. The epigraph he puts at the head of chapter XX is "Even the clearest and most perfect circumstantial evidence is likely to be at fault." He heads the chapter of circumstantial evidence with a warning against it, and then supplies the one kind of evidence that is not.

What beginners get wrong

They say Wilson denies the prosecution's case. He grants its central claim, and that is the point.

They say he calls an expert. He is the expert, and he asks to be sworn and to testify himself, but the comparisons are made by the jury.

They think the finger-prints only identify the murderer. They also prove the exchange in the cradle, which is what turns an acquittal into a tragedy.

They forget the two children. A and B, at five, seven and eight months, are the second half of the proof and the half candidates omit.

A worked answer

Question. MU's own: "Discuss in detail the evidences presented by Puddn'head Wilson."

Paragraph one, the position. Wilson wins by conceding the prosecution's central claim and then proving that it destroys their case rather than his, and his evidence is of one kind only: finger-prints, made usable by enlargement and verified by the jury themselves.

Paragraph two, the concession. The prosecution urged persistently that the person whose blood-stained finger-prints were on the knife handle was the murderer. Wilson rose and granted it, to general astonishment, because once granted, the prosecution's own proposition acquits his clients the moment the prints are shown to be somebody else's.

Paragraph three, the explanation before the proof. He told the court that every human being carries from cradle to grave physical marks that never change, a physiological autograph that cannot be counterfeited, disguised, hidden or worn away by time, and which is not the face, the hair, the height or the form, because duplicates of all of those exist.

Paragraph four, the method. He had made pantograph enlargements ten times the natural size on white cardboard, with every line reinforced in ink, so that patterns which look identical to the naked eye can be distinguished across a courtroom. He then handed the foreman a magnifying glass and made the jury do every comparison.

Paragraph five, the four comparisons. The accused men's prints against the window panes: identical. The same against the knife handle: exactly identical. The accused men's prints against the assassin's: they do not even resemble. And then the infant records of two children marked A and B, tallying at five and seven months and not at eight, which proves that the children were exchanged in the cradle, followed by A's print at the age of twelve against the knife: to the minutest detail.

Paragraph six, the honest qualification. Not everything Wilson said was proved. Twain tells the reader that the motive of robbery, the person in the room beforehand and the figure in woman's clothes at the back gate were hardy guesses hazarded to fill gaps, and that Wilson watched Tom's face to see whether they had hit. A full answer separates the proof from the bluff, because the chapter is a study of advocacy and not only of science.

Quick revision

Prosecution: the twins' knife, found in the room, bloody prints on the handle left by the murderer, the twins standing over the body, motive, and the unclaimed reward.

Wilson grants that the prints on the handle are the murderer's.

He explains the physiological autograph: unchanging from cradle to grave, not counterfeitable, not the face or hair or height or form.

He enlarges the records ten times with a pantograph and inks the lines.

The jury compare: the twins' prints match the window panes, and do not even resemble the knife.

The infant records of A and B tally at five and seven months and not at eight: the children were exchanged in the cradle.

A's print at twelve matches the knife to the minutest detail. Tom faints, and Wilson says he has confessed.

Test yourself

1. Why does Wilson concede the prosecution's main claim? Because it makes their case depend entirely on the prints being the twins'. Once he shows the prints are somebody else's, the prosecution's own proposition proves his clients innocent.

2. What does Wilson mean by a physiological autograph? The pattern on the ball of a finger, which he says every human being carries from cradle to grave, which does not change, which cannot be counterfeited, disguised, hidden or worn away, and of which there is no duplicate among all the people in the world.

3. How does he make the evidence usable by a jury? By enlarging his glass-plate records ten times with a pantograph onto white cardboard and inking every line, so that patterns can be distinguished at a distance, and then having the jurymen make each comparison themselves with a magnifying glass.

4. What do the records of children A and B prove? That each child's prints at five and seven months tally with each other, that neither tallies with the print taken at eight months of the child bearing the same letter, and therefore that the two children were exchanged in the cradle between seven and eight months.

5. Distinguish what Wilson proved from what he guessed. Proved: that the knife prints are not the twins', that they are Tom's, and that the children were exchanged. Guessed: that the motive was robbery, that somebody was in the room before the twins, and that the figure at the back gate was a man in woman's clothes. Twain says the guesses were hazarded to fill gaps, and that Wilson watched Tom's face to see whether they had hit.