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[Bob Mueller]

So I've got a teen-aged girl murdered in late May in NE Louisiana (Monroe area). Doesn't matter to my story if she's actually buried, or just left above ground. Body isn't found for several weeks, but I can adjust that as needed.

Temps at the time are mid to upper 80s, with very high humidity (90 - 100%). Perhaps 1.5 inches of rain over a three-week period. BTW, Weather Underground is a VERY handy site if you're interested in historical weather data.

About how long until she's down to mostly bones, with little noticeable or DNA-useful flesh?

How does hair decompose? I'd like some brown hair to be left on her head.

How long until DNA is not easily recoverable for identification purposes? I'm thinking of 2007 technology. The body has no ID; the murderer identifies her as a particular person, who is indeed missing, but her mom is missing, and her father is unknown at the time. What I want is for the body to be identified based on DNA on the underwear found on/near her.

Yes, I'm working towards the body being identified as the wrong person, using just the underwear and the murderer's identification.

[Dave Freas]

Hi, Bob.

According to what I've picked up from my forensic anthropologist daughter, your teenage girl would be just about bones given the time frame and weather conditions you describe.  I'll see if still have an article on decomp. she sent me some time ago.  I'd say if you have the girl undiscovered for 4 weeks, you'd be safe.

You victim will decay slightly faster if buried as bugs in the ground will have easier access to her.  If she's left above ground, you run into the problem of wildlife--foxes, wolves, raccoons, whatever carnivores or omnivores are indigenous to NE Louisiana--snacking on the body.  Think animal buffet.  And don't forget dogs!  Little known fact: Dogs on the loose are one of the prime discoverers of bodies.  Carnivores will tear her open to get at the internal organs and gnaw off fingers, toes, hands, and feet and carry them off for a midnight snack.

You don't need flesh to get DNA.  If the girl's long bones are intact, you can get DNA from the marrow (I think) and you can get it from the teeth, too.

Hair is a different story.  Being basically keratin, it does not decompose like living tissue.  It practically lasts forever.  After 4 weeks, your girl's hair would be pretty much intact unless the critters snacking on her carried it off with the flesh they pulled off her skull.

Hope this helps.

Dave

[Bob Mueller]

Yes, it does; thanks. The hair part is a big thing, since there's no one to point out that they ID'd a brown-haired girl as a blond-haired girl.

I knew about the dog thing, but hadn't really considered how it could help me. I may end up doing this as partial remains; that could make things a little easier on the mis-identification issue.

After 4 weeks or so, the hair would just be in clumps, right? The scalp would have decomposed by then?

[Dave Freas]

After 4 weeks or so, the hair would just be in clumps, right? The scalp would have decomposed by then?

There might be a few clumps attached to some scraps of scalp (bet you can't say 'scraps of scalp' five times fast) or caught under the skull.  There also may be some clumps that are just tangles of loose hair, but many individual hairs may have gotten scattered by the wind and some clumps may have been carried off by scavengers.

Dave

[Bob Mueller]

This has been very helpful so far Dave. Now a question for your daughter.

A bit more background: Two teen girls were kidnapped, and the kidnapper has told investigators that he killed them, and buried them in shallow graves. He eventually led investigators to these graves. Both girls were about 13, around 5 feet tall, and blondes.

I'd like to know more about estimating the height of an incomplete skeleton. Let's assume "They found...part of one femur, parts of the other tibia and fibula. It looks like...most of the ribs. All six major arm bones." Also an incomplete skull - mandible is gone. Pelvic girdle is basically intact, as is the clavicle.

I'd like a plausible way to make the height estimation way off, by six inches or more.

I've got a dead adult male to deal with, as well as the two girls. What about mixing in some of the adult male's bones? I know the major bones (femur, tib/fib, radius, etc) can be gender-identified, right? Are there any bones I could mix in to throw things off?

[Dave Freas]

A bit more background: Two teen girls were kidnapped, and the kidnapper has told investigators that he killed them, and buried them in shallow graves. He eventually led investigators to these graves. Both girls were about 13, around 5 feet tall, and blondes.
I'd like to know more about estimating the height of an incomplete skeleton. Let's assume "They found...part of one femur, parts of the other tibia and fibula. It looks like...most of the ribs. All six major arm bones." Also an incomplete skull - mandible is gone. Pelvic girdle is basically intact, as is the clavicle.
I'd like a plausible way to make the height estimation way off, by six inches or more.

The femur is the 'core bone' used in calculating height estimates based on tables a forensic anthropologist would consult.  There is a fairly fixed ratio between the length of the femur and the height of the person.  With only part of a femur, I doubt they would even hazard a guess.  The arm bones can be used, but the estimate of height would be much broader.  The incomplete skull would help with the age estimate (based on the degree of fusing of the sutures between the bones), but the pelvic girdle in a 13 y. o. female would not be differentiated enough from a 13 y. o. male for an anthropologist to say 'female' definitely.  At most, the anthro would say, "This person is probably female."

I've got a dead adult male to deal with, as well as the two girls. What about mixing in some of the adult male's bones? I know the major bones (femur, tib/fib, radius, etc) can be gender-identified, right? Are there any bones I could mix in to throw things off?

Some of this would depend on the build of the male.  If he's six-five and two-ninety, no way would his bones be taken for those of a 5 foot 13 year old female.  If he is just out of puberty, short and fairly slender and light of build (gracile in anthro-speak), his bones might be initially taken as female, but on closer look would be identified as adult male.
The give away is not the bones themselves, but some of the details of the bones.  Adult male bones are usually more robust overall than female and have bigger protuberances where muscles attach.
The determination of age is based on the presence or absence of epiphyses (spongy areas in long bones where growth occurs).  In a 13 y. o. female's bones, they would be easily visible.  In a 40 y. o. male, they would have disappeared.  In a 21 y. o. male, they may be present or absent or somewhere in between.
A rib from a gracile 21 y.o. male might be taken for one from a 13 y.o. female on first look, but close examination would probably reveal it as male.

Much of this is dependent on the build of the individual.  Bones from a robust female may easily be mistaken for those of a gracile male.  The fewer bones (and the fewer major bones--femur, tibia, fibula, ulna, radius, humerus) recovered, the harder it will be to pin down sex, approximate age, and approximate stature of the individual.

Hope this helps.

Dave

[Dave Freas]

A follow-up:

I'll shoot your post(s) to my daughter, see if (a) I got it right and (b) she has anything to add.

It may take a few days for her to get back to me.

Dave

[Dave Freas]

...Dave finally gets back to you.

Hi, Bob.

Had a chance to talk to my daughter the other day and touched on this with her.

The one big thing she said was that any competent anthropologist, even most students, would immediately be able to tell an adult male bone (gracile or not--I was wrong on that) from those of a 13 year old girl just by looking at them.

Perhaps you could throw things off by having the (egotistical? pompous? overbearing?) ME make the wrong call on the bones--saying they're all from the 13 year olds--thus delaying identification of some of the bones as male.

Will pass on more as I get it.

Hope this helps.

Dave

[Bob Mueller]

Very helpful, as always Dave!

I'm pretty much going to lay the mis-identification at the feet of the state crime lab, but anything the murderer could do to throw things off would help, too.

The lab and investigators hosed up three identifications. There were three girls kidnapped. There were three bodies found; the killer told the cops that A, B, and C were buried here, here, and here. What the killer actually did was to kidnap three runaways (C, D, and E), kill & bury them. The original kidnap victims were shipped out to a South American slavery ring. The three original victims were all blondes, and about the same age & size. At the moment, I've pointed out that brown hair was found at all three graves, and most of the bodies were incomplete; I'll explain that away by animal activity. I thought about having the killer dismember the bodies, but didn't want to deal with saw marks on the bones.

Is there anything the killer could do or add to the bodies that would speed decomposition, but not be very obvious to investigators? Maybe a way to attract wildlife?

This has been a huge, huge help!

[Dave Freas]

Is there anything the killer could do or add to the bodies that would speed decomposition, but not be very obvious to investigators? Maybe a way to attract wildlife?

First off, glad I (and my daughter) could help.

As far a speeding decomp, you've probably put the bodies in the best possible environment for it.  Bodies decompose fastest in a warm, damp environment.  Upper 80s with 90-100% humidity is about as good as it gets.
Leaving the bodies atop the ground would make them more accessable to predators than if they were buried.  No need to attract wildlife.  The odors of decomp will do that just fine without any human help.

Dave