Profiles work best when the offender displays obvious psychopathology, such as sadistic torture, postmortem mutilation, or pedophilia. Some killers leave a "signature"—a behavioral manifestation of an individualizing personality quirk, such as positioning the corpse for humiliating exposure, postmortem biting, or tying ligatures with a complicated knot. This helps to link crime scenes and may point toward other types of behaviors to look for.

What a profile can offer that's helpful are the offender's general age range, racial identity, ideas about the modus operandi, estimates about living situation and education level, travel patterns, the possibility of a criminal or psychiatric record, and probable psychological traits. A profile may also describe a fantasy scenario that drives the person or even pinpoint an area where he or she probably resides. This is all based on deductions about the specific crime from what is already known about offenders and deviancy.

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The best profilers have gained their knowledge from experience with criminals and have developed an intuitive sense about certain types of crime. Their knowledge base is developed from both physical and nonphysical evidence. Generally, profilers employ psychological theories that provide ways to detect mental deficiency such as delusions, spot imprints from hostility, recognize criminal thought patterns, and predict the right character defects. They also need to know about actuarial data such as the age range into which offenders generally fall and how important an unstable family history is to criminality. Much of that information came from actual cases, such as the following.