A religious person is he who abides by certain principles in service to the mankind. Christ has also sad that that man is super who is at service to the human beings and creatures on earth. A police officer too is a person who must abide by law and serve the people with dedication to safeguard their rights. The instinct of service and dedication to his job inspired him to leave some guidelines for those who have to join police service or are in service. On completion of 39 years of service in the Delhi Police, author thought of writing a book on Police Investigation: Law and Procedure on the basis of his personal experiences and difficulties faced during the service. Not only did he work as an investigating officer in the police stations, but also as an officer in-charge of a number of police stations, sub-divisions and in the Crime Branch of Delhi Police. In this book, he has tried to cover all aspects of police investigation, law and procedure. He has dwelt on recording of FIRs, investigation in cognizable cases, powers of the investigating officers, searches, seizures, remands, identification of accused, confessions, etc. Law regarding the constitutional rights of accused, grant of bails also has been explained in detail. Of late, dowry deaths have become quite common and as such investigation in dowry death cases, crime against women including kidnapping, abduction, rape, indecent representation of women, outraging the modesty of a woman has been explained. The investigating officer has to face many difficulties and as such he must be aware of his powers and limitations, particularly with reference to arrest, power to summon witnesses, remand, unlawful assemblies, harbouring of offenders, escape from police custody, etc. Chapters on scientific aids to the investigation and model FIRs have been added in this book. Every effort has been made to make this book educative so as to make the investigating officers knowledgeable about their functions, powers and limitations. We hope that the supervisory and investigating officers will find this book quite useful.