Most of the serial killers that are caught have very high rates directly tied to them, it becomes impossible to maintain the constructed life as they become more out of control or the construct becomes too elaborate in the face of too much evidence, Bundy, Chikatilov, Green River, Gacy, Dahmer, there always becomes a time where the evidence becomes beyond their control. These guys are more successful though, they are less likely to come from abnormal upbringing, the criminal profile that they have points to a larger cross section of society, normality, this control they have and the larger base of potential suspects allows them to operate over a larger period of time. In respect to their partners they are able to exert more subtle emotional control and dont have to rely on physical or particularly overt abusive behaviour.

Most unsolved serial murders involve less than 10 victims directly attributed to them spaced out over longer periods of time, exceptions to the rule of period of course, Zodiac, highway of tears, colonial parkway killer, redhead murderer, alphabet murders, freeway phantom, long island killer. west mesa bone collector, bible john, it starts to creep up a little with rainbow maniac, monster of florence, boston strangler etc, but almost exclusively under 15 always. There are a number of factors that may have stopped them, death, disability, incarceration etc. But i think its about control/control of evidence against them.

Those that do get caught with lower body count are more likely to come from an abnormal childhood, they are less able to control their behaviour and this will give a criminal profile that points to a smaller section of section of society, abnormality. they are more likely to be sexually violent or introduce sexually violent themes and physical abuse to a relationship.