Fingerprints and a crime

The_Ink_Goddess said:

This is mostly an "is this plausible?" question rather than "how does this work?"

This might seem incredibly dumb of me, sorry. I know very little about forensics.

So, essentially: criminal leaves fingerprint behind while committing a murder that will be dismissed as a bizarre freak accident. When she dies in suspicious circumstances, someone who loves buries her body, cleans off all her fingerprints from everything, and amputates her hands to prevent her fingerprints from going into a database and being matched to the crime. Even though they do conceal her body, they amputate her hands specifically so that some accidental unearthing of her body (let's say, through real estate development), can't match her fingerprints.

But - do fingerprints come from DNA? So if you had an effectively handless person with no way to cross reference from anything, could you still match their fingerprints (and their fingerprints alone) to their body? (I need the answer to be no, but I thoroughly understand if it's a yes .) Also, is it possible to commit a crime and leave only fingerprints, and no other DNA, behind?

Thank you!

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I'm a liiiitle confused -- someone commits a murder, then dies, then someone ELSE, who neither committed the murder or killed the murderer, chops the hands off the murderer and buries her?

If I get your q. correctly, no, you can't like, magic up what someone's fingerprints would look like from a DNA sample. Fun fact: identical twins have identical DNA profiles, but different, individual fingerprints, because the individuality of fingerprints is, in part, created by fetal interaction with the interior of the womb. When you press your forming fetal fingers against the inside of the amniotic sac against the wall of the uterus, that (when/pressure/where/etc.) helps determine the formation of your fingerprints.

That said, if someone wants her fingerprints, they exist. If I want your fingerprints, they're all over your house, your car, your desk, etc. It's very hard to remove all traces of someone's fingerprints. Spend an hour when you go home paying attention to everything you touch.

It's possible to leave just a fingerprint behind (if you're careful and good) but fingerprints contain DNA, so....

Hang on, what system? Who is taking DNA from her fingerprints? That's a process; you have to do it intentionally. I mean there's hoards of DNA all over your tshirt (more than your hairbrush actually -- I am a font of fun forensic facts today), but someone has to actually want to find it, if you see what I'm saying.

Oh, I just noticed your location. You may be screwed, yes. I'm not positive of the specifics of the databases and interaction of various departments and what is done and input. Ask someone familiar with the LOCAL procedure there. Someone still has to want to get DNA from the print tho.

Here the whole 'database' thing is a royal mess of localities, feds, intersection and not, overlap and gaps, etc. Hence my original q.

Let's discuss the many ways of identifying a body. Understand that one, or two methods may be combined and many are not absolute, but can be reliable.

1. Fingerprints
2. DNA
3. Facial recognition and reconstruction
4. Dental records
5. X-rays, CAT scans, and other medical tests
6. Blood type
7. Tattoos, scars, birth marks, and other marks on the body
8. Hair (one of the last things to decompose)
9. Shoe size
10. Elimination of other possible people
11. Clothing
12. Skeletal size

In other words, virtually anything can be used.

Let's take a skeleton found buried, no skin or soft tissue remaining. We'll have an approximate height from the skeleton, as well as limb lengths. A bit of hair can tell us hair color, even if there is no DNA possible. Person hadn't been to the dentist in thirty years, but the dental record matches with additional work and missing teeth. Person had not broken any bones and had no other defects. Facial reconstruction matched last picture of possible victim. Person went missing 20 years ago and body appears to have been in the ground for about 10 years.

Bodies in this state have received what is viewed as a positive identification.

Cutting off the hands doesn't preclude a positive identification, but merely slows down the process.

I realize this doesn't directly answer your question, but gives you an idea of everything that can be looked at.

Jim Clark-Dawe

Given all this, it may be better for the person to burn her house down with her body inside. Then again the fire will be investigated and there may be enough of her remains left to tell that she was already dead.

CWatts said:

Given all this, it may be better for the person to burn her house down with her body inside. Then again the fire will be investigated and there may be enough of her remains left to tell that she was already dead.

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That's a common thing tried and it fails. It's nearly impossible to destroy a body, or even come close, with a house fire. Crematoriums run thousands of degrees and still have bone and other solids left over. House fires leave tons of evidence, including whether the person was alive when the fire started, and often how the person died in the first place.

The_Ink_Goddess said:

So, essentially: criminal leaves fingerprint behind while committing a murder that will be dismissed as a bizarre freak accident. When she dies in suspicious circumstances,

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?????? When who dies?

caw

cornflake said:

That's a common thing tried and it fails. It's nearly impossible to destroy a body, or even come close, with a house fire. Crematoriums run thousands of degrees and still have bone and other solids left over. House fires leave tons of evidence, including whether the person was alive when the fire started, and often how the person died in the first place.

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That is precisely why my unfortunate victims tend to end up under International waters via a long boat ride or off the ramp of a C130.

cornflake said:

That's a common thing tried and it fails. It's nearly impossible to destroy a body, or even come close, with a house fire. Crematoriums run thousands of degrees and still have bone and other solids left over. House fires leave tons of evidence, including whether the person was alive when the fire started, and often how the person died in the first place.

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Bit of trivia left over from my semester of forensic anthropology:

Bones don't burn. Period.

If I remember my chemistry correctly, basically things burn because there's energy left in them that can be released or used to fuel the fire or something, I'm fuzzy on this part but I do remember combustion being a release of energy. Bones don't have that energy, or don't have enough of it to become ash.

Bones burn. Really truly. You just need a hot enough fire lasting long enough. s.v. crematorium.

JetFueledCar said:

Bit of trivia left over from my semester of forensic anthropology:

Bones don't burn. Period.

If I remember my chemistry correctly, basically things burn because there's energy left in them that can be released or used to fuel the fire or something, I'm fuzzy on this part but I do remember combustion being a release of energy. Bones don't have that energy, or don't have enough of it to become ash.

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I dunno what forensic anthropologist said that, but either he or she was confused or you maybe misunderstood, because sure bones burn. They're hard to burn entirely, but they'll burn. They've got lots of fat inside them; regardless, you can burn a desiccated skeleton in a hot enough fire.

cornflake said:

you can burn a desiccated skeleton in a hot enough fire.

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You're all deeply disturbing people - you know that, right?

JetFueledCar said:

Bit of trivia left over from my semester of forensic anthropology:

Bones don't burn. Period.

If I remember my chemistry correctly, basically things burn because there's energy left in them that can be released or used to fuel the fire or something, I'm fuzzy on this part but I do remember combustion being a release of energy. Bones don't have that energy, or don't have enough of it to become ash.

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Even solid metal burns at a hot enough temperature. You can even get a noble gas to react at high enough pressures and temperatures.

This looked useful: NIH: Forensic trace DNA: a review

You could have the story occur in a year prior to trace (touch) DNA testing developments.


A separate issue (a concern of mine unrelated to the OP but related to trace DNA) to keep in mind on this subject, trace DNA has the potential to pick up false positives and it's dangerous to assume every microscopic DNA fragment collected comes from a perpetrator. We think of DNA as scientific, objective, yadda yadda. But that is fraught with unresolved issues when it comes to trace DNA.

Does the trace DNA from an unknown source found in the victim's underwear absolve the suspect, or is it possible that is DNA from handling in the manufacture or distribution of the clothing?

mccardey said:

You're all deeply disturbing people - you know that, right?

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O

Did you know, given the right conditions, a body can skeletonize and bleach in as little as three weeks? Under 'normal' conditons, that can take years, but put a body out in the right environment and it can be very quick, which can fool the heck out of all but the most experienced experts.

MaeZe said:

This looked useful: NIH: Forensic trace DNA: a review

You could have the story occur in a year prior to trace (touch) DNA testing developments.

A separate issue (a concern of mine unrelated to the OP but related to trace DNA) to keep in mind on this subject, trace DNA has the potential to pick up false positives and it's dangerous to assume every microscopic DNA fragment collected comes from a perpetrator. We think of DNA as scientific, objective, yadda yadda. But that is fraught with unresolved issues when it comes to trace DNA.

Does the trace DNA from an unknown source found in the victim's underwear absolve the suspect, or is it possible that is DNA from handling in the manufacture or distribution of the clothing?

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Of course it's possible. Now if someone could just inform the Boulder PD...

If the issue is removal of fingerprints, obliterating the fingertips through proper application of household chemicals might do the trick of obscuring them. Also, fingerprint matching tends to be very very hard, not like how it's shown on TV.

1: How clear was the fingerprint at the original crime scene? Fingerprints are often smudged, or did not leave a clear, full print (partials, as you hear talked about on TV).

2: Is there anything else linking her to the original crime, so that when they discovered a body with unusable fingerprints, other means of discovery would link her? Because there are many ways to identify a body, but if the goal is to break the link to the original crime, then removing her hands or destroying her fingerprints would make the people who found the body suspicious that _something_ was up, but the link to the original murder would be successfully obscured.

cornflake said:

... Of course it's possible. Now if someone could just inform the Boulder PD...

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I tried to leave that out of my post lest it totally sidetrack the thread, but the case you mention is exactly the one I had in mind. It is debatable whether the trace DNA of an unknown male exonerated anyone*. (*I cannot vouch for the validity of the rebuttal claims, I did look at papers like this original research review of the contamination problem.

Contamination is a crucial issue in the analysis and interpretation of trace DNA. Contaminant DNA may appear as either the major or minor sample within a mixture or, alternatively, may overwhelm the target DNA completely. From a theoretical perspective, any DNA deposit that is not immediately relevant to the crime being investigated can be viewed as contamination. In this light, gross or sporadic contamination may appear at any point: (1) before the crime has been committed; (2) in the interval between the crime and securing the crime scene; (3) during the investigation of the scene; and/or (4) within the laboratory.

The first point can be viewed as the level of background DNA present under normal circumstances [88, 201, 202].

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)

I had a debate about this issue in another forum. Some otherwise critical thinkers fixated on the idea objective DNA was unassailable evidence. I investigated and discovered trace DNA has been found in brand new, not yet out of the package underwear. The courts have a long way to go if they want to properly establish the conditions with which this evidence should be admissible, and it will be unfortunate if a new potential evidentiary mistake replaces others such as false confessions and fallible eye-witnesses.

Great material for a crime story though.

The idea it was anyone but her parents (or brother, covered up by the parents), given the circumstances of that scene and the aftermath, are fairly unbelievable, and always have been.