w5 3a

Forensic Tools: What’s Reliable and What’s Not-So-Scientific Share:

For years, American TV shows have featured crime scene investigators using forensic evidence to solve grim mur-

ders. Often, however, these fictional CSIs present unrealistic portrayals of the capabilities of forensic science.

The reality is that not all forensic evidence is backed up by rigorous scientific research – meaning it doesn’t al-

ways point to the person who “did it.” A landmark 2009 study by the National Academy of Sciences

(http://www.nap.edu/catalog.php?record_id=12589) (NAS) highlighted the tools that work – and those that fall

short. Here’s a sampling of the basics:

DNA Analysis is the Gold Standard

In 1984, a British geneticist named Alec Jeffreys stumbled upon one of our most important forensic tools

(http://news.bbc.co.uk/2/hi/programmes/newsnight/8245312.stm): DNA fingerprinting. Since his “eureka mo-

ment,” the scientific technique has been used successfully to identify perpetrators of a crime, clarify paternity

and exonerate people wrongly convicted.

A P R I L 1 7, 2 0 1 2

by Jonathan Jones (https://www.pbs.org/wgbh/frontline/person/jonathan-jones/)•

M E N U (http://www.pba.org/)

Today, the testing and analysis of DNA is considered the most reliable of all of the forensic tools. Unlike many of

the others gathered to meet the needs of law enforcement, it faced rigorous scientific experimentation and vali-

dation prior to its use in forensic science.

“Among the biggest problems that we uncovered in the report is the absence of the application of scientific

methodology to determine whether or not the discipline was valid and reliable as was done with DNA,” says

Harry T. Edwards (/wgbh/pages/frontline/criminal-justice/real-csi/judge-harry-t-edwards-how-reliable-is-foren-

sic-evidence-in-court/), a U.S. federal judge and part of the NAS committee that produced that 2009 report.

“DNA is really the only discipline among the forensic disciplines that consistently produces results that you can

rely on with a fair level of confidence, when you’re seeking to determine whether or not a piece of evidence is

connected with a particular source.”

In fact, DNA has actually called into question the reliability of other forensic sciences, says Innocence Project co-

founder Peter Neufeld.

“When we looked at all the cases of people who have been exonerated by DNA evidence

(http://www.innocenceproject.org/know/), we found that in 60 percent of those cases, experts who testified for

the prosecution produced either invalid evidence or the misapplication of science in their testimony.”

Fingerprints Can Lie

For more than a century, fingerprints, palm prints and sole prints have been used as identification tools by law

enforcement. Collectively known as “friction ridge analysis,” this forensic method involves examiners comparing

the details of an unknown print with a set or a database of known prints. These details include ridges, loops,

whorls and other points of similarities.

Criminologists and law enforcement officials long swore that fingerprint identification was infallible and that it

was possible for an examiner to determine that a print comes from a single unambiguous source. If an examiner

has a whole, perfect print, they argued, identifications can be made with reliability.

But recent errors have fueled a debate about the reliability of fingerprint forensic evidence, the most prominent

being the case of Oregon lawyer Brandon Mayfield. After the March 2004 terrorist bombings in Madrid that

killed almost 200 people, a partial print found on a bag of detonators was sent to the FBI. An examiner deter-

mined that the print belonged to Mayfield, who was later detained. In total, four fingerprint examiners – includ-

ing one hired by Mayfield’s defense team – declared that his print matched the partial from Spain.

M E N U

Except there was a problem (http://www.nytimes.com/2004/05/25/us/bomb-case-against-lawyer-is-

rejected.html?ref=brandonmayfield): the print wasn’t Mayfield’s at all. Spanish officials matched the partial print

to an Algerian man named Daoud Ouhnane. Mayfield later sued the government, which settled for $2 million

(http://www.washingtonpost.com/wp-dyn/content/article/2006/11/29/AR2006112901179.html).

“I knew that our profession had taken some sort of a quantum leap because suddenly there were new rules in-

volved,” veteran fingerprint examiner Ken Moses told FRONTLINE. Moses was one of the four people who incor-

rectly matched Mayfield to the latent print.

According to the National Academies of Sciences, no peer reviewed scientific studies have ever been done to

prove the basic assumption that every person’s fingerprint is unique. Recent studies have also shown that finger-

print examiners can be influenced by contextual bias (/wgbh/pages/frontline/criminal-justice/real-csi/can-uncon-

scious-bias-undermine-fingerprint-analysis/) when comparing fingerprints.

“Prior to Mayfield, there were some people in the fingerprint community who really were saying that something

like Mayfield could never happen,” says Jennifer Mnookin, a UCLA law professor who is leading a federally-

funded study of error rates in fingerprint comparisons. “And so part of the problem here really is about hubris or

over-claiming. It’s about a field that didn’t seem to feel a need to recognize its limits.”

FBI fingerprint expert Melissa Gische told FRONTLINE that, as a result of cases like Mayfield’s, she would no

longer testify to a zero error rate for fingerprints in court.

Sometimes Bite Marks Bite Back

One of the most controversial forensic techniques is bite-mark comparison. Bite marks can change over time and

be distorted due to factors like swelling and healing. Similar to fingerprint analysis, the assumption behind bite

mark comparisons that every person’s dental characteristics are unique has not been adequately scientifically

studied or scrutinized.

M E N U

Attorneys for the Innocence Project say that the scarcity of research backing up bite mark comparisons played a

role in a number of wrongful convictions over the years.

“There have been a number of people who were convicted based on bite-mark testimony who were sent to

death row or sent to prison for life,” says Neufeld, who represented both Levon Brooks

(http://www.innocenceproject.org/Content/Levon_Brooks.php) and Kennedy Brewer

(http://www.innocenceproject.org/Content/Kennedy_Brewer.php), both wrongly convicted based in large part on

faulty bite mark testimony (http://reason.com/archives/2007/10/08/csi-mississippi). “And in each of those cases, a

whole group of forensic odontologists, forensic dentists said they were absolutely certain that this was the guy

and they were absolutely wrong.”

Firearms, Bullets and Ballistic Identification

When shots are fired in the commission of crime, a forensic expert is often brought in to study the trajectory of

the bullets; later, he or she may testify in court as to the direction from which a bullet came and the firearm used

in the crime.

The National Academies of Sciences recognized the logic involved in trying to compare firearms-related marks by

noting, “although they are subject to numerous sources of variability, firearms-related tool marks are not com- pletely random and volatile; one can find similar marks on bullets and cartridge cases from the same gun.” But

the NAS also observed, that “the validity of the fundamental assumptions of uniqueness and reproducibility of

firearms-related tool marks has not yet been fully demonstrated.”

The report added that, “a significant amount of research would be needed to scientifically determine the degree to which firearms-related toolmarks are unique or even to quantitatively characterize the probability of

uniqueness.”

M E N U

One fundamental problem with firearms analysis is the lack of a precisely defined process, the NAS found. An ex-

aminer may offer an opinion that a specific tool or firearm was the source of a specific mark when “sufficient

agreement” exists in the pattern of two sets of marks, but there is no precise definition for that statement. The

NAS also found there have been no scientific studies to answer questions regarding variability, reliability, re-

peatability, or the number of correlations needed to achieve a given degree of confidence.

Matching Hair is Not as Simple as Splitting Hairs

For years, forensic hair examiners have testified that physical characteristics of hairs can be identified and used

to establish the presence, or absence, of certain people at a crime scene.

The problem? No scientifically-accepted statistics exist about the frequency with which particular characteristics

of hair are distributed in the population, according to the NAS. And there appears to be no uniform standards on

the number of matching features that must be present for an examiner to declare a match.

Recent studies reveal that microscopic hair analysis is not yet a precise science. One study by the FBI, cited in the

NAS report, found that of 80 hair comparisons done through microscopic examinations, 9 of them, about 12.5

percent, were found to come from different sources when reexamined through DNA analysis.

For more, read this Washington Post investigation (http://www.washingtonpost.com/local/crime/convicted-de-

fendants-left-uninformed-of-forensic-flaws-found-by-justice-dept/2012/04/16/gIQAWTcgMT_story.html) on how

problematic hair and fiber analysis may have led to wrongful convictions.

Where There’s Smoke There’s Not Necessarily Fire

When a fire occurs, fire investigators are called to the scene to determine the cause of the fire and the potential

for arson.

But according to the National Academies of Sciences, a lot more research is needed on the natural variability of

burn patterns and damage characteristics and how they are affected by the presence of various accelerants. In

fact, as FRONTLINE reported in the 2010 film Death by Fire (/wgbh/pages/frontline/death-by-fire/), many of the

supposed telltale signs of arson – the remnants of accelerant pour patterns, for example – can actually be caused

by natural phenomena during accidental fires.

“The fire investigation community largely consists of people who are firemen. They’re not scientists,” arson ex-

pert John Lentini told FRONTLINE. “Extinguishing a fire and investigating a fire involve two different skill sets

and two different mindsets.”

Another scientific expert, Gerald Hurst (/wgbh/pages/frontline/death-by-fire/interviews/gerald-hurst.html), of-

fered a startling “devil’s advocate” opinion about the state of arson testimony in the courtroom: ” I could take al-

most any fire and — if I were so inclined — convince a jury that it was arson. It’s frighteningly simple, frighten-

ingly easy.”

M E N U

Lentini’s website Scientific Fire Analysis hosts his breakthrough publications

(http://www.firescientist.com/publications.php) on arson science, including “The Lime Street Fire: Another

Perspective (http://www.firescientist.com/Documents/TheLimeStreetFire-AnotherPerspective.pdf),” [PDF] which

contests traditional understandings of burn patterns through a series of tests.

Watch this excerpt from Death by Fire for more on the emergence of new fire science — and how it called into

question the guilt of Cameron Todd Willingham

(http://www.newyorker.com/reporting/2009/09/07/090907fa_fact_grann), who was executed in 2004 after being

found guilty of the arson-murder of his three young children:

There is Solid Science Behind Drug Testing

Also known as forensic toxicology, the analysis of controlled substances involves the collection of chemicals that

have the legally recognized potential for abuse. They include “street drugs” such as heroin and ecstasy, and pre-

scription drugs like oxycodone.

Drug testing is the most frequent forensic function performed by publicly funded crime laboratories, which ana-

lyze biological samples for the presence of toxins present in an individual to determine whether the amount of

those substances is above a harmful level. It is used to make inferences on an individual’s death, illness, and men-

tal or physical impairment. Like DNA analysis, the analysis of controlled substances is a mature forensic science

discipline and one of the areas with strong scientific underpinnings developed along the lines of classical analyti-

cal chemistry.

M E N U

Learn more (https://www.pbs.org/about/faqs/online- sponsorship/)

WATC H T H E D O C U M E N TA R Y

The Real CSI (https://www.pbs.org/wgbh/frontline/film/real- csi/)

S U P P O R T P R O V I D E D BY

SEE WHAT FRONTLINE IS WORKING ON NOW

Your email address

Your zip code

G E T O U R N E W S L E T T E R

The NAS report found that there exists an adequate understanding of the uncertainties and potential errors in

the analysis of controlled substances due to rigorous scientific testing.

Jonathan Jones (https://www.pbs.org/wgbh/frontline/person/jonathan-jones/)

Journalistic Standards (https://www.pbs.org/wgbh/frontline/about-us/editorial-standards-and-ethics)

(https://www.pbs.org/wgbh/frontline/film/real-csi/)

M E N U

Shake-Up Inside Forensic Credentialing Organization (https://www.pbs.org/wgbh/frontline/article/shake-up- inside-forensic-credentialing-organization/) A P R I L 1 1 , 2 0 1 4

Can Juries Rely on Forensic Experts? (https://www.pbs.org/wgbh/frontline/article/can-juries-rely-on-forensic- experts/) S E P T E M B E R 5, 2 0 1 3

Mississippi Doctor's Autopsies at Center of Wrongful Conviction Filings (https://www.pbs.org/wgbh/frontline/article/mississippi-doctors-autopsies-at-center-of-wrongful-conviction- filings/) J A N U A R Y 8 , 2 0 1 3

R E L AT E D A R T I C L E S

TO P I C S

Criminal Justice (https://www.pbs.org/wgbh/frontline/topic/criminal-justice/)

M O R E S T O R I E S

S H O W C O M M E N T S

M E N U

N E X T O N F R O N T L I N E

A Rare Look Inside Police Training in Utah (https://www.pbs.org/wgbh/frontline/article/video-police- training-utah-shots-fired-documentary/)

How might police training impact whom, when and why officers

shoot? Watch an excerpt from the new FRONTLINE/Salt Lake

Tribune documentary “Shots Fired.”

N O V E M B E R 2 3 , 2 0 2 1

Is the Fear Factor Overblown in Police Shootings? (https://www.pbs.org/wgbh/frontline/article/police- shootings-fear-factor/)

Utah’s police training has been questioned for focusing on

worst-case scenarios.

N O V E M B E R 2 2 , 2 0 2 1

Kids and Climate Change: Who's Learning What — or Not — and Why? (https://www.pbs.org/wgbh/frontline/article/cop26-kids- climate-change-miseducation-book/)

As COP26 wraps, the new book 'Miseducation: How Climate

Change Is Taught in America' and past stories from former

FRONTLINE reporter Katie Worth offer more context.

N O V E M B E R 1 2 , 2 0 2 1

No Taper Tantrum & Other Recent Federal Reserve News, Explained (https://www.pbs.org/wgbh/frontline/article/no- taper-tantrum-quarles-resignation-federal-reserve/)

To make sense of it all, here’s a closer look at news that has

broken since the FRONTLINE documentary "The Power of the

Fed" first aired in July 2021 and what it means.

N O V E M B E R 1 0, 2 0 2 1

(https://www.pbs.org/wgbh/frontline/article/video-police- training-utah-shots-fired-documentary/)

(https://www.pbs.org/wgbh/frontline/article/police-shootings- fear-factor/)

(https://www.pbs.org/wgbh/frontline/article/cop26-kids- climate-change-miseducation-book/)

(https://www.pbs.org/wgbh/frontline/article/no-taper-tantrum- quarles-resignation-federal-reserve/)

S H O W M O R E ( H T T P S : // W W W. P B S .O R G / W G B H / F R O N T L I N E /A R T I C L E S / )

Poor Kids

F E B R U A R Y 1 1 , 2 0 1 3

M E N U

G E T O U R N E W S L E T T E R

Your email address

S U B S C R I B E

F O L L O W F R O N T L I N E

Home (https://www.pbs.org/wgbh/frontline/)

Films (https://www.pbs.org/wgbh/frontline/films/)

Podcasts (https://www.pbs.org/wgbh/frontline/podcasts/dispatch/)

Investigations (https://www.pbs.org/wgbh/frontline/investigations/)

Schedule (https://www.pbs.org/wgbh/frontline/schedule/)

Contact Us (https://www.pbs.org/wgbh/frontline/about-us/contact-us/)

Our Funders (https://www.pbs.org/wgbh/frontline/about-us/our- funders/)

Privacy Policy (https://www.pbs.org/wgbh/frontline/about-us/privacy- policy/)

PBS Privacy Policy (https://www.pbs.org/about/pbs-privacy-policy/)

PBS Terms of Use (https://www.pbs.org/about/terms-use/)

Corporate Sponsorship (https://www.sgptv.org/programs/PBS-frontline/)

About Us (https://www.pbs.org/wgbh/frontline/about-us/)

History (https://www.pbs.org/wgbh/frontline/about-us/history/)

Awards (https://www.pbs.org/wgbh/frontline/about-us/awards/)

Editorial Standards and Ethics (https://www.pbs.org/wgbh/frontline/about-us/editorial-standards-and- ethics/)

Journalistic Guidelines (https://www.pbs.org/wgbh/frontline/about- us/journalistic-guidelines/)

Senior Editorial Team (https://www.pbs.org/wgbh/frontline/about- us/senior-editorial-team/)

Our Staff (https://www.pbs.org/wgbh/frontline/about-us/our-staff/)

Jobs/Internships (https://www.pbs.org/wgbh/frontline/about-us/jobs/)

Pressroom (https://www.pbs.org/wgbh/frontline/topic/announcements/)

PBS LearningMedia (https://www.pbslearningmedia.org/collection/fl/)

FRONTLINE Teacher Center (https://www.pbs.org/wgbh/pages/frontline/teach/)

Jon and Jo Ann Hagler on behalf of the Jon L. Hagler Foundation

Koo and Patricia Yuen

(https://www.wgbh.org/support/directed

A B O U T

O U R T E A M

_ _ _ _ _ _

_ _ _ _ _ _

T E A C H E R C E N T E R

,

M E N U

(https://www.pbs.org/) (https://cpb.org/) (https://www.fordfoundation.org/)

(https://www.abramsfoundation.org/) (https://www.macfound.org/) (http://www.parkfoundation.org/)

Funding for FRONTLINE is provided through the support of PBS viewers and by the Corporation for Public Broadcasting. Major funding for FRONTLINE is provided by the Ford Foundation. Additional funding is provided by the Abrams Foundation; the John D. and Catherine T. MacArthur Foundation; Park Foundation; and the FRONTLINE Journalism Fund with major support from Jon and Jo Ann Hagler on behalf of the Jon L. Hagler Foundation, and additional support from Koo and Patricia Yuen.

FRONTLINE is a registered trademark of WGBH Educational Foundation. Web Site Copyright ©1995-2021 WGBH Educational Foundation. PBS is a 501(c)(3) not-for-profit organization.

M E N U