Tag Archives: forensic

Blood Can Run, But It Can’t Hide

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Camera

 

Bloodstains are really tough to eradicate. Tiny drops of spatter patiently wait on walls for luminol to uncover them. Blood seeps into carpet padding, behind baseboards, and inside of drains.

Now, forensic scientists in Australia show that even paint cannot hide bloodstains. Rachel Ehrenberg’s Science News article, “Camera Hack Can Spot Cleaned-up Crimes,” describes how infrared photography can reveal blood hidden under paint. Even six layers of black paint could not hide blood spatter. The article includes tips by a specialist in art conservation and imaging about the type of paint a murderer might use to cover a crime.

Fish Finger

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Fingerprint

 

During September, Nolan Calvin and Mark Blackstone went fishing at Priest Lake, Idaho. They were cleaning a trout when they discovered something unusual: a human finger. The fisherman placed the finger on ice and brought the digit to a local police station. Investigators obtained a fingerprint from the finger; it belonged to Hans Galassi, who had lost the fingers from his left hand during a wakeboarding accident in June. Galassi had no use for the retrieved finger.

As BBC News notes in the article, “Who What Why: How durable is a fingerprint?” fingerprints can last a long time and are tough to get rid of. The article is a good source for basic information about the durability of fingerprints and attempts to obliterate those pesky friction ridges.

Who Are You? – Revisited

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SNPs

 

Several weeks ago, I described research at Israel’s Tel-Hai Academic College, which may enable investigators to create a rough portrait of a person from DNA. In the August/September 2012 issue of Forensic Magazine, Timothy D. Kupferschmid provides background information about this type of technology.

Kupferschmid, executive director of Sorenson Forensics, explains that early attempts at forensic phenotyping (i.e., creating a portrait from DNA) used DNA analysis to determine gender, and to predict hair and eye color. Sorenson Forensics developed a DNA test to predict a person’ genetic ancestry. The test relies upon the observation that, during the course of human history, portions of the DNA of human populations living in geographically isolated regions became slightly distinct from the DNA of human populations in other regions. Certain DNA markers are associated with five populations: Western European, Western Sub-Saharan African, East Asian, Indigenous American, and residents of the Indian Subcontinent. As Kupferschmid emphasizes, the test does not reveal “ethnicity” or “race,” which are social concepts that geneticists consider to be arbitrary and without scientific foundation.

You can find details about this new aid for criminal investigations in Kupferschmid’s article, “Forensic Phenotyping: the 21st Century Composite Sketch.” The investigators of your mystery story will thank you.

Arrestee DNA Law on Trial

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Arrestee-DNA

During the late 1980s, Colorado enacted the first US DNA databank law, a law that required sex offenders to provide a DNA sample to law enforcement officials. This was based on the theory that a person convicted of a sex offense was likely to repeat the crime, and therefore, quick access to a DNA profile could identify a repeat offender. Other states enacted DNA laws, expanding the categories of individuals who must donate a DNA sample. Today, all states require the collection of DNA from sex offenders, and most states collect DNA from felony offenders. Many states obtain DNA from juveniles convicted of certain crimes and from individuals convicted of certain misdemeanors. Some states also require collection of DNA from probationers and parolees.

Taking DNA from persons arrested for certain crimes remains controversial. The federal government and about half of the states have laws that allow DNA sampling before conviction. Courts have ruled on both sides of the issue. In 2006, for example, the Minnesota court of appeals ruled that an individual’s privacy interests trumped the state’s interest in analyzing DNA. The court decided that portions of the state’s DNA law “that direct law-enforcement personnel to take a biological specimen from a person who has been charged but not convicted violate the Fourth Amendment to the United States Constitution and Article I, Section 10 of the Minnesota Constitution.” Other courts have approved arrestee DNA collection laws, and supporters of the laws assert that the laws increase the efficiency of criminal investigations and save lives.

Now, the issue is headed toward the US Supreme Court. The case began in 2009 when Maryland police arrested Alonzo Jay King for first-degree assault. Following Maryland’s DNA Collection Act, personnel at the booking facility collected King’s DNA. Analysis revealed that it matched DNA evidence from a rape committed in 2003. Based on this hit, the State charged and convicted King of first degree rape. He was sentenced to life in prison. King appealed the conviction. The Maryland Court of Appeals, the state’s highest court, overturned King’s conviction, holding that the collection of his DNA violated the Fourth Amendment, because his expectation of privacy outweighed the State’s interests. Maryland appealed the decision to the Supreme Court.

During July 2012, Chief Justice Roberts indicated that the Court will probably take the appeal. He also said that “given the considered analysis of courts on the other side of the split, there is a fair prospect that this Court will reverse the decision below.” Taking arrestee DNA may be here to stay.