The identification and classification of Subtypes in psychopathy

Criminal psychology study is often associated with psychopathy, researchers have increasing knowledge about psychopathy as larger numbers of research are done. However, subtypes of psychopathy are still a controversial area as it is still arguable if the subtypes exist, and there are no clear definition and classification criteria. Currently there are a few opinions suggesting either two subtypes or four subtypes of psychopathy, but due to limitation of information provided, neither of these methods were adopted.
Introduce possible subtypes of psychopathy according to the few suggestions given and analyse the experiment methodology, then suggest a better classification of psychopathy subtypes.