This book describes how to use logic, reasoning, critical thinking, and the scientific method to conduct and improve criminal and civil investigations. The author discusses how investigators and attorneys can avoid assumptions and false premises and instead make valid deductions, inductions, and inferences. He explains how tools such as interview and interrogation can be used to detect deception and profile unknown individuals and suspects. The book is aimed at improving not only the conduct of investigations, but also the logical use of cognitive, analytical, documentation, and presentation tools to win cases.