Computer crime is becoming more commonplace and more severe with today's rapid evolution of technology. Almost every law enforcement agency in the world deals with cybercrime every single day on local, national, and even global levels. It is vital for law enforcement agencies to have the experience and expertise necessary to tackle these problems.
Where a law enforcement agency would seek assistance with computer crime investigations depends on how large the investigation is and how large the law enforcement agency is. For example, the Federal Bureau of Investigation (FBI) is the top federal agency for investigating cybercrime in the U.S. and overseas. That being said, the FBI can assist other law enforcement agencies locally and abroad in their cybercrime investigations. The FBI may handle cybercrime on a much larger scale, but local law enforcement can seek their help if they need it.
Law enforcement agencies have also been known to contract outside assistance from computer experts. You may have seen a police department in a crime drama meet with an expert to gather information that would be helpful to their investigation. Even though the show is probably largely fictional, that does happen in real life. There are individual experts and even entire investigative corporations who specialize in cybercrime everywhere, and it is not uncommon for law enforcement to seek their help.