5. Conclusion
This systematic review is not without its limitations. First, the two groups of sexual murderers analyzed were distinguished on the basis of the number of murder victims. The data obtained for this variable were extracted from police files, and, in the case of nonserial murderers, were subject to two biases. While the group of serial sexual murderers is composed of individuals found guilty of at least three murders, the group of nonserial murderers may include serial sexual murderers
whose subsequent victims were not identified, as well as potential serial sexual murderers whose early apprehension prevented them from accumulating further victims. Second, some of the studies on sexual murderers did not discriminate between serial and nonserial mur-derers. Third, although there is no empirical evidence of differences between sexual murderers of adult women and sexual murderers of children, it would have been ideal had the data discriminated between murderers on the basis of the age of their victims. Fourth, the harmoni-zation of variable labels across studies may have resulted in some loss of information. Finally, this systematic review was essentially limited to North American studies, and its results may not be representative of sexual murderers around the world.
Future research could focus on international comparisons, in order to determine whether sexual murderers from different countries pos-sess different characteristics. A common research protocol would facili-tate research of this type.
In summary, NSMs and SSMs exhibit distinct characteristics, and these shape their sexual crimes. Thus, sexuality and sadism are at the heart of SSMs' homicides. These murderers are socially isolated, re-jected, and humiliated, and take refuge in compulsive masturbation and paraphilias in order to compensate for the poverty of their emotion-al, relational, and sexual lives. In contrast, NSMs are polymorphic crim-inals who are easily angered when their immediate needs are not satisfied. They adopt a victim stance, and sexual homicide is for them a form of vengeance, an outlet for their anger. These two profiles are consistent with the classification of Beauregard and Proulx (2002), which identified a group of sadistic sexual murderers and a group of angry sexual murderers, corresponding to SSMs and NSMs respectively. Finally, this systematic review has shown that the dramatic murders paraded before the public in the media on a regular basis are in fact rep-resentative only of SSMs, who in fact account for a low proportion of all sexual murderers.