Always look at the evidence at a scene without any bias, or preconceived notions about anyone, you have to let the evidence do the talking.
The one sure fire way to screw up an investigation is to try to make someone fit the crime, you could have 10 serial killers living withing 300 yards, of a crime scene that doesn't mean they were responsible for the crime you are investigating , you have to examine each piece and ask "why is this here?"
In abduction murders which is what this is, the offender usually lives or works in the area ,in this case, the victim as last at a basketball game after school and was waiting for her mother to pick her up
Its rare you see a child abducted from school grounds because theres so many eyes about , this would be an extremely high risk for the offender to be riding around a school and grab a victim, this would lead be to believe he was comfortable there and wasn't worried about being seen.
Most abductions take place relatively close to the victims home, (.5 mi) usually on their way home, or to school
And though we have the image of the boogeyman waiting behind a bush who jumps out and grabs a child, its only slightly more prevalent that the individual is a stranger to the victim. (52% stranger)
Its not all that uncommon that the victim knows their killer in these cases.
We need to know via victimology study what type of kid Debbie was, was she trusting and naive, was she reckless, did anything change in the days or weeks prior to her murder, did she ever mention anything to anyone that may have been bothering her , where was she waiting for her mother , inside , outside?,
Would she have gotten onto a car, with someone she didnt know?, was she naive, and easliy duped ?
There's a hundred questions you have to ask about the victim, to better understand those who prey on them
The manner of death is extreme for a 10 year old, stabbed 19 times, seems to indicate possibly a personal connection (anger/rejection) and an inexperienced offender.
However Stabbing of the face is very telling, disfiguring is an attempt to "destroy" the persons image , its indicative of rage , and anger that's often associated with personal interests of the offender.
This wasn't just disposing of someone, there was a message being relayed from killer to victim.
Those interests could range from sexual to financial etc, but in the case, of an abducted 10 year old girl, i don't think you have to be Sherlock Holmes to put this one together.
Though sexual assault wasn't identified , it doesn't mean it wasn't a motivating factor in this case, in abduction murders, the overwhelming motive is sexual.
The mean age of the offender in abduction murders of children is around 27 years old, that can change slightly but most are between 26 and 36 years old when they commit their first offense
The offender who is unknown to the victim, usually lives with parents, when the victim is known to the offender, they may be married or in some type of arrangement with a significant other.
The unknown individual usually has a history of crimes involving children, the known offender will usually have some criminal past, but not always indicative of sexual predation.
The offense usually is not planned, its an impulsive act , as I feel this was as well, theres usually little preparation prior to.
I read somewhere that there were no defensive wounds on Debbie's body, with no indication of the victim being bound , that to me indicates, she was comfortable with whomever she was with, that she didnt expect the physical assault .
The offender in theses cases, will revisit the victims body about 85% of the time within 48 hours, and multiple times after, if the body hasn't been discovered, which is why I tell people to come forward if they have ever seen an individual around the area where a body is discovered, especially if its prior to it being discovered there .
"yeah I had a close call once I had gone back to where she was when i went to leave, my car got stuck in the mud on a soft shoulder, i was there panicking, then someone eventually came along and helped, me out, they had no idea a body was just a few feet from them " -This was never reported by those who helped the killer get his car out of the mud
The unknown offender (stranger) usually has a history of frequent moves, and relocates often, usually within a year of the offense.
In these cases, the name of the person responsible usually is known to LE within about a week, theres just something that prevents us from pinning it on him, and with what as available to investigators in the 60's many cases, would go unsolved, because before we could link via DNA, some departments wouldn't know what to do with it back then and in some cases, evidence like DNA was simply disregarded .... not saying this is the case, in Debbie's murder, just saying that back then it was old gumshoe work .
More often than not in these cases, theres someone who knew or strongly suspected the person responsible but said nothing in some cases, they confessed to it , and even in some cases, the other person, helped dispose of evidence, in some cases, the victim themselves .
As for Polygraph tests, the polygraph is a great tool if its used by a competent examiner, for those who don't know polygraphs don't detect lies, they detect, physiological changes in response to questions. Im sure most know that already, but you have to understand that biological issues with certain individuals can produce false reads.
Whats more telling is that one individual was brought in for 6 tests, and agreed to do so 6 times and also failed all 6 .
The problem with multiple Polygraph tests, is that a defense attorney can swing it either way, "youre harassing my client that's why he failed", "Several tests means LE isn't sure about the tests".... And as we all know people can eventually come to grips with what they did and pass a polygraph if they have enough time .
That's why you need a good examiner, and you take 1 test, not multiple, though nowadays polygraph examiners are so good they have much more success, especially the ones from the CIA, they are the best
I personally think LE was on the right track with this individual, but something happened and the case went cold.
And one more thing, don't think because someone has been "cleared" , let go, ruled out, or even acquitted, that they didnt do it, our system is flawed, lets not forget a certain professional athlete that despite a mountain of evidence against him in the brutal death of 2 individuals, 1 being the mother of his children, was let go on a technicality, BUT was later found guilty of BOTH their deaths in a civil trial later on, meaning he did it and got away with it, could never face jail time because of it , he just had to pay money.
There are limitations to the law, our system is broken, it lets bad people out over and over, and unfortunately despite evidence sometimes people get away with murder, because the rules are set against LE , not those responsible, but that's the way it is unfortunately.