Livor Mortis: The Science of Death

by Marianne English

iStockphoto

Pathologists and medical examiners piece together how and when a person likely died. Fleshing out these details clue investigation teams into whether a person succumbed to natural causes, an accident or by the actions of someone else. But to make accurate estimates of time of death, they need to understand the science behind body reactions once the heart stops beating.

Though there are many factors to consider, livor mortis, a phenomenon involving the shift of blood in the body, is often examined alongside other types of clues such as rigor mortis, or muscle stiffness.

Every second, a living person's heart pumps oxygen-rich blood through the entire body in an extensive network of veins, arteries and capillaries. Blood gives organs and muscles the nutrients and warmth they need to work properly.

But what happens when the heart stops pushing blood throughout the body, and why does it matter to scientists?

For starters, the blood stops moving and gravity takes hold. If a person dies and falls on his back, blood will settle in the areas closest to the ground and will slowly drain from the body's front side. Indeed, such movement gives the dead the pale appearance we associate with a lack of life. Blood doesn't disappear, it simply moves to the backside of the body closest to the ground.

As death settles in, the blood begins to congeal, making the back of the person's body purple and pink from the influx of blood. After eight to 12 hours, the blood will usually stay that way.

But the parts of the body in direct contact with objects or the floor will appear pale because of the pressure placed on the skin's capillaries. One medical examiner and pathologist at a lecture on forensics and murder explains that when you press and hold your fingertip on the top of your hand for a few seconds, you'll release it to find it's paler than your surrounding skin. Then, it quickly turns back to your normal skin color. This is because your body recirculates the blood you temporarily pushed away.

The same concept applies when livor mortis sets in, except there's no heartbeat to push blood back into parts of the body.

 

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Handprints May Give Away Height, Gender

The technique relies on the fact that taller people, and men, tend to have larger hands than shorter people and women.

  by Anna Salleh, ABC Science Online

Hand prints can reveal a person's height and size (Getty Images)

Prints left by the hand, or even parts of it, can be used to estimate the height of an unknown intruder and possibly tell whether they were male or female, say researchers.

A team led by forensic anthropologist Associate Professor Daniel Franklin, from the University of Western Australia, report their findings in a series of recent scientific papers.

"That might be useful if you've got someone who has broken into a house or someone has been seen messing around with a window of a house," says Franklin.

When trying to identify a suspected perpetrator of crime experts try to narrow down the list of potential suspects.

... The researchers took measurements of 91 male and 100 female adults from Western Australia. They measured the height of each individual and took seven measurements of each hand and its corresponding print.

Franklin and colleagues measured hand breadth and length, palm length, as well as the length of the first, second, third and fourth digits.

They then carried out a statistical analysis and found that hand prints involving these parts of the hand could be used to estimate height.

"If you're taller you tend to have longer limbs and you tend to have bigger hands as well. It's a scaling effect," says Franklin.

"We can show that there is a strong correlation between the size of your hand and your ... height and the same thing applies to a print from a hand."

Franklin says a forensic investigator could use these statistics to get a quantifiable estimate of an offender's height and this would help narrow down suspect profiles given out to the public or could be used to narrow down a given list of suspects.

Franklin says the study showed hand prints can predict height with a relatively high degree of accuracy, close to that of height predictions from hand bones.

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Trayvon Martin 911 Call: How Experts ID Voices Voice recognition software can show the actual speech structure of the vocal cords to make a match.

 by  Sheila Eldred

Have you ever realized how different your voice sounds on an answering machine? This week, Kasey-Dee Gardner finds out which one is your "true" voice and why.

In classic whodunnit mysteries, detectives and FBI agents dust for fingerprints to solve mysteries and collect court-admissible evidence.

In real life, it's more often the voice that offers the tell-tale evidence, since technology to recognize voices in recordings has become so much more sophisticated.

The Feb. 26 recording of a 911 call by a woman who reported someone crying out for help in her gated community in Sanford, Fla., could be a key piece of evidence in the Trayvon Martin murder case, especially since she called early enough so that screams for help and the gunshot were recorded.

George Zimmerman, a Neighborhood Watch volunteer, shot Martin, an unarmed 17-year-old. Why he did so remains a hotly argued topic, with Zimmerman claiming Martin attacked and beat him.

Tom Owen, a forensic consultant for Owen Forensic Services LLC and chair emeritus for the American Board of Recorded Evidence, recently analyzed the tape. After running the woman's 911 call through a software program called Easy Voice Biometrics and comparing it to another 911 call with Zimmerman's voice, Owen's team concluded that the screams for help were not Zimmerman's.

And, Owen said, if he had samples of Martin's voice, he may be able to definitively identify the screams as his.

"We've talked to the family; the attorney has been notified," he told Discovery News.

How can he be so sure?

...  "The human voice is like a symphony, each voice is unique based on the type of instruments played and skill of the musicians playing the instruments. Similarly, the human voice is created using many physical components, the lungs, larynx and wind pipe. These exit the body through the mouth involving our tongue, teeth and lips," Primeau said.

"As forensic experts, we do not have the proper tools to arrive at a positive ID to conclude the voice is Trayvon yelling for help," Primeau said. "By process of elimination, both Tom and I agree the voice yelling is not Zimmerman. That is our opinion."

Trayvon Martin's brother has said that the screams on the tape sound like his brother.

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