A criminal defense lawyer is a lawyer specializing in the defense of individuals and companies charged with criminal conduct. Criminal defense lawyers can be permanently employed by the various jurisdictions with criminal courts. Such lawyers are often called public defenders. For a much more extensive discussion of criminal defense, see public defender. The terminology is imprecise because each jurisdiction may have different practices with various levels of input from state and federal law or consent decrees. Other jurisdictions use a rotating system of appointments with judges appointing a private practice attorney or firm for each case.

In the United States, criminal defense lawyers deal with the issues surrounding the apprehension, searches of client or property, and arrest of his or her client (Fourth Amendment), as well as any statements the client may have made. (Fifth Amendment). Criminal defense lawyers also deal with the substantive issues of the crimes with which his or her clients are charged. In the United States criminal defendants are entitled to the presumption of innocence until prosecutors prove each essential element of a crime beyond a reasonable doubt. Serious crimes (e.g. felonies) in the United States are tried to juries of twelve people and the jury must be unanimous in its verdict to either convict or acquit the defendant. A split in the jury is often called a "hung jury" and may result in a retrial of the defendant. Criminal defense lawyers actively pursue their client's cause through all stages of a criminal prosecution.