( CNN ) -- In television dramas like CBS ' `` Criminal Minds , '' serial killers are apprehended swiftly and surely . In real murder cases -- as in the investigation and recent capture of a suspect in the so-called `` Grim Sleeper '' killings on the south side of Los Angeles , California -- it can take years , even decades , to bring a suspect to justice . Police are now saying that the arrest of 57-year-old Lonnie David Franklin Jr. closes the book on at least 11 unsolved murders that occurred since 1985 . Unlike most homicides , which are solved in a matter of days , if not hours , crimes committed by a prolific serial offender present a daunting challenge to investigators . There is an element of self-selection : Only those perpetrators who possess the right level of skill , street savvy or cunning can remain at large long enough to amass a large victim count and , therefore , achieve the status of serial killer . A careless wannabe would likely be stopped long before that point , and certainly before reaching double digits as did the Grim Sleeper . However , the difficulties that homicide detectives confront when searching for unidentified serial murderers are not so much about their being `` master criminals '' -- as most are not -- but about their usual offense pattern and modus operandi . Several factors common among serial murderers and their crimes work in their favor and tend to keep their identity a mystery : . 1 . Serial murderers usually target strangers -- those who happen to be at the wrong place at the wrong time and who are selected either out of sheer convenience or because they fit the killers ' fantasies and murder script . Thus , the standard investigative approach used by homicide detectives of assembling a list of likely suspects ( friends , neighbors , and co-workers , anyone with a reason to kill the victim ) does n't help in the least . The killer could be just about anyone with whom the victims came in contact . And when the victims live off the streets , like some of the women slain by the Grim Sleeper , the list of possible suspects can be endless . 2 . Serial killers generally dispose of their victims ' bodies in remote or otherwise hidden places -- a river , a wooded area , or even in large garbage bags tossed in trash bins . As a result , the police do n't have an evidence-rich crime scene ( where the victims were assaulted ) to scour for clues . The disposal site tends to yield very little in the way of physical evidence , especially if it is exposed to the elements or wildlife . 3 . Serial killers tend to be ordinary in appearance , looking above suspicion . Like the man arrested in connection with the Grim Sleeper murders , they just do n't fit our stereotype of a vicious killer . People are usually incredulous when they learn the allegation of their neighbor 's hidden activities . In fact , the seemingly trustworthy veneer that aids serial killers in attracting victims into their grasp also serves them well in appearing anything but suspicious . In addition , their detailed planning process often includes conjuring up a host of plausible alibis should the police come knocking at the door . 4 . Serial killers , like the Grim Sleeper , tend to prefer vulnerable people as targets , especially prostitutes , drug users or other marginal types whose disappearance will not generally bring a massive police effort or strong community response . Also , those on the street who might be in a position to witness the abduction of a prostitute or drug user do not generally make for cooperative and reliable witnesses . For all of these reasons , serial killers , when eventually discovered , are often captured because of luck -- bad luck on their part and terrific luck for the rest of us . In the Grim Sleeper case , police used a discarded slice of pizza to get Franklin 's DNA , which they linked to evidence at some of the crime scenes , sources told The Los Angeles Times . And sometimes , serial killers just get a bit too overconfident after years and years of eluding law enforcement and begin to see themselves as unstoppable . At that point , they frequently become careless and take unnecessary risks . Ultimately , their own arrogance becomes their downfall . Despite the challenges that serial murder cases pose for homicide investigators , there are certain strategies that can maximize the chances of solving a case , even when the trail grows cold with passing years . Although DNA evidence did not produce any direct hits to a suspect , the Los Angeles police went the extra mile by checking indirect familial DNA matches . After linking genetic material to a prisoner , circumstantial evidence led investigators to the inmate 's father -- Lonnie David Franklin Jr. -- the Times reported . But often the secret to success is nothing as intricate or intriguing as the various scientific tools featured on CSI-Wherever . Rather , it entails old-fashioned approaches such as canvassing the neighborhood , interviewing witnesses and preparing detailed investigative reports . Most of all , successful serial murder investigations require skilled management of personnel and information . When the body count rises , so does the volume of leads that need to be pursued and number of officers involved in the manhunt . The key to solving a seemingly unsolvable crime often comes down to administrative efficiency , as well as to that little stroke of welcome luck . The opinions expressed in this commentary are solely those of James Alan Fox .
Serial killers often elude capture for years due to nature of their crimes , says James Alan Fox . He says they are hard to identify because they lack obvious ties to the victims . Fox says in many cases there is no crime scene available for analysis . Comment: