Getting the Ax

pickaxe

 

It won’t inspire an episode for a high-tech forensic TV show, but it’s still a good detective story.

On March 15, Michelle Hunter reported a crime on The Times-Picayune website, a burglary of a New Orleans pharmacy. Somebody had chiseled a hole through the store’s cinderblock wall and crawled through. The burglar left with a load of narcotics, but left a pickaxe behind. The pickaxe had a price sticker from a nearby home improvement store.

Detective Darrin Parent brought the tool to the improvement store, where staff scanned the barcode to determine when and where the axe had been purchased. With this information, they checked the store’s video surveillance footage to watch a man purchase the pickaxe.

An owner of a store near the burgled pharmacy contacted Detective Parent. On the night of the crime, his CCTV camera had captured images of the same man around the time of the burglary. The video footage also recorded the license plate number of the vehicle driven by the suspect.

Warrant in hand, Detective Parent visited the suspect’s house, where he found drugs stolen from the pharmacy. An arrest followed for burglary and drug possession.

DNA and Killer Twins

DNA

 

A criminal who has an identical twin poses a problem: Identical twins arise from identical DNA. The microenvironment of a developing embryo affects the formation of fingerprint patterns. As a result, identical twins (who developed in different microenvironments) have different fingerprints. What happens when a savvy criminal does not leave fingerprints at a crime scene?

Barry Starr of QUEST Northern California tackled this question in his posting entitled, “Genetic Sleuthing, or How to Catch the Right Identical Twin Criminal.” Starr highlights a sexual assault case in Marseille, France. Using video evidence and standard DNA analyses, police identified two suspects who are identical twins. Which twin is the guilty one?

DNA can offer one way to distinguish between a set of identical twins. Twins begin life with identical DNA, but DNA changes. One type of change is called an epigenetic change. “Epigenetic” refers to changes in DNA that affect gene activity without altering nucleotide sequences in DNA. Researchers have found different epigenetic markers in the DNA of identical twins. DNA mutations, caused by chemicals and UV light, also cause small changes in DNA. Why didn’t police in Marseille rush to order DNA tests for epigenetic markers and mutations? The cost of one million euros to perform the tests discouraged that approach.

If you’re planning to include a killer twin in your story, peruse the comments to Starr’s article. You’ll find plenty of ideas about how your investigators might tackle the problem.

The Problem of False Convictions

Characteristics in cases that led to erroneous convictions and cases that led to near misses.

Characteristics in cases that led to erroneous convictions and cases that led to near misses. Source: Jon B. Gould et al., Predicting Erroneous Convictions: A Social Science Approach to Miscarriages of Justice. Final report to the National Institute of Justice (February 2013).

 

The National Institute of Justice funded American University researchers to study factors that lead to wrongful convictions. They examined 460 cases of violent felonies that occurred from 1980 to 2012, and they asked the question: Why are some innocent people convicted while others are released?

This month, the NIJ posted the final report. Gould and his colleagues identified 10 factors that led to a wrongful conviction:

  • A younger defendant
  • A defendant with a criminal history
  • A weak prosecution case
  • Prosecution withheld evidence
  • Lying by a non-eyewitness
  • Unintentional witness misidentification
  • Misinterpreting forensic evidence at trial
  • A weak defense
  • Defendant offered a family witness
  • A “punitive” state culture – defined by the number of executions per population.

In addition to the report, the NIJ offers videos of Jon Gould explaining the study.