THE present work was the first really objective Criminal Psychology which dealt with the mental states of judges, experts, jury, witnesses, etc., as well as with the mental states of criminals. And a study of the former is just as needful as a study of the latter. The need has fortunately since been recognized and several studies of special topics treated in this book—e.g. depositions of witnesses, perception, the pathoformic lie, superstition, probability, sensory illusions, inference, sexual differences, etc.—have become the subjects of a considerable literature, referred to in our second edition.

I agreed with much pleasure to the proposition of the American Institute of Criminal Law and Criminology to have the book translated. I am proud of the opportunity to address Americans and Englishmen in their language. We of the German countries recognize the intellectual achievements of America and are well aware how much Americans can teach us.

I can only hope that the translation will justify itself by its usefulness to the legal profession.

Hans Gross.