Abstract This article discusses several implementations of modern technology in criminal investigations and the ethical issues that accompany these techniques, focusing on the trade-off between security and privacy. Specific topics include information centralization, telecommunications, and general technology. Cases are cited for each topic, along with a discussion of the ethical issues involved. With the advent of modern technology, the face of criminal investigation, and even daily life, has been irrevocably changed. In addition to easily locating criminals, authorities now have the ability to monitor potential criminals before they commit crimes. However, with increased detection capability comes an inevitable trade-off in privacy. Monitoring society as a whole means monitoring both the innocent and the guilty. Phases of sudden change involve a period of social adjustment, including debates centered on the 4th Amendment and privacy. 4th Amendment cases reflect the difficult application of 200-year-old principles to a changing society as they examine the trade-off between privacy and protection. Despite a large number of high-profile cases involving general technology and criminal investigations, the majority of advances in the field have been undeniably beneficial to the law enforcement community. Ballistics, the study of projectile dynamics, has helped authorities track down countless criminals. By maintaining a record of the types, sources and characteristics of firearms and ammunition, investigators have an invaluable tool for gathering information about crimes. The recent advent of DNA tests and analyzes allows for indisputable identification of individuals. Traces as small as fingernails, hair or skin cells can place an individual at the scene of a crime. Police officers equipped with laptops can instantly look up a vehicle's history, including whether it was reported stolen or belonged to someone with outstanding warrants. Many innovations have undoubtedly facilitated criminal investigations without causing controversy. However, a multitude of technologies have prompted privacy advocates to be overly sensitive. Centralization of information is a concept that has sparked debate. Large databases can contain information about an entire state or country, something that has been done for years in paper form. The difference is that when information takes electronic form, its location is often indeterminate and the data is subject to corruption or hacking. Given the ability to integrate information about an individual into a single record, there is cause for concern about misuse..