>Cordelia Willis


>Solving Crimes in the Future




>Sherlock Holmes used a magnifying glass and fingerprints; today's

>crime-solvers use capillary electrophoresis and DNA. How has

>technology changed the way crimes are investigated and solved?

>Are TV shows like CSI accurately portraying how forensic

>scientists work, or are they a gross exaggeration of real life?

>What does the future hold in store?


>Cordelia Willis is a Criminalist with the Santa Clara County Crime

>Laboratory and knows firsthand how technology is constantly

>affecting how cases are worked. She will explain how DNA and

>other new techniques can now solve cases that were unsolvable

>twenty years ago, as well as discussing their limitations.



Willis began her talk by explaining that Criminalists are basically laboratory people. Sometimes they collect evidence at crime scenes and sometimes the police bring them evidence. They spend a lot of time comparing known samples (for example blood from a suspect) with unknown samples (for example blood from a crime scene). They also testify in court about what they have found in the lab.

Then she explained some of the things Criminalists don't do. They don't do background investigations or interview witnesses (police detectives do that kind of work). They don't carry guns (at least in Santa Clara County, for some jurisdictions that is different). They don't wear stylish clothes because it is important to be able to wash the stuff after a day of working with hazardous chemicals and crawling around in dumpsters looking for evidence.

One of the things that has changed over the past couple of decades is that the number of online databases available has mushroomed from nothing to just about everything you could ask for. Willis listed databases for fingerprints, firearms, shoes, and DNA of convicted felons. Willis illustrated how they were used with the OJ Simpson case, where footprints left at the scene of the crime turned out to be size 11 Bruno Mali Italian shoes. She also explained that the fingerprint database will give the data seeker a short list, but it is still necessary for an expert to go through the data to find a certain match, and spent some time on the minutia of that work.

Willis began her comments about the role of the media by saying that anything that builds interest in the field is great. She became a Criminalist because she wanted to be like Scully on the X Files. The biggest difference between the TV version of her work and the real thing is that they compress everything. On TV, the expert glances into the microscope and says "they match!" In real life, an expert spends eight hours staring at the data and then says "I think they match, but I have to check again in the morning to be sure." Also, real life cases have a lot more drudgery of examining things like body fluids left on dirty underwear than TV shows.

A decade ago, when DNA evidence was new, every time they used it in a courtroom they had to explain every detail of the procedure to the Judges, lawyers, and Jury. Now that most of the judges understand it, the DNA evidence comes up, the prosecutor asks "Did it match?", and the Criminalist says "Yes." End of story. Sometimes, when they have to testify in some place like San Mateo County where the legal system is five to seven years behind ours, they still find Judges that need to have it explained occasionally.

During Q&A, Willis explained that Santa Clara County has a full service crime lab with a staff of something like 54 people, 32 of whom are Criminalists. Sometimes they do analysis for investigations in San Mateo, Santa Cruz, and Monterey Counties as well as our own.

Tian Harter



a) Prove or disprove pre-existing investigative theories

b) Provide legal proof in the courts

c) Occasionally assist in development of suspects

d) Assist in the collection of physical evidence at crime scenes


Evidence that can potentially be identified as originating from a single

source (individual characteristics):


--firearms / toolmarks

--shoeprints / tiremarks

--physical matches

--questioned documents (handwriting)

--biological evidence (DNA)

Evidence that can be associated with a group rather than a single source

(class characteristics &/or material identification):

--trace (glass, paint, hair, fibers)

--arson evidence

--drugs (controlled substances)


--biological evidence (blood, semen, saliva, etc.)


Evidence and reference samples are subjected to the same tests and

examinations to determine if they have a common origin.

Essential materials for comparative examinations:

Reference sample = sample from a known source;


--blood samples from a victim or suspect (for DNA)

--glass from point of entry of burglary scene

--paint from a suspected hit-and-run vehicle

--shoes from a suspect

--writing exemplars from a victim or suspect

Control sample = sample from an uncontaminated area located near the

evidence item; the purpose is to determine if the substrate will contribute

or interfere with the examination and to ensure that the techniques are

working properly.


--Fingerprint Development (no comparisons performed)

--Firearms Examinations

a) firearms identification via comparison of fired projectiles and cartridge


b) make and model determination of type of firearm used

c) functional examinations (to determine if a firearm is functioning


d) silencer examinations

e) distance determinations

f) trajectory reconstructions

g) serial number restorations

h) gunshot residue analysis

i) entry into IBIS (Integrated Ballistics Identification System)

--Toolmarks Comparisons

ex. crowbars, screwdrivers, pliers, bolt cutters, staple guns

--Shoeprints / Tiremarks Comparisons

--Physical Matches

Physical matches of randomly torn paper or broken edges can establish with

absolute certainty that two or more objects once formed a single item.

--Questioned Documents

a) examination of handwriting, typewriting, mechanical printing, papers, and


b) comparisons to exemplars = multiple handwriting samples from suspect

which duplicate the questioned document's form, writing utensil, style of

writing (i.e., print vs. cursive), and contents

c) examination of indented writing using ESDA (ElectroStatic Detection


--Biological Evidence

a) identification of body fluids (e.g., blood, semen, saliva)

b) DNA analysis, comparisons, and identifications using PCR / STRs from the

following types of evidence: blood; semen; penile swabs; condoms; saliva

(envelope flaps, cigarette butts, bite marks, etc.); urine; hair roots;

tissue (skin, organ, etc.); bone; teeth; fingernail scrapings

c) searches of unknown DNA profiles with CODIS (FBI's COmbined DNA Indexing


--Trace Evidence

a) glass

b) paint

c) hair - human and animal

d) fibers

--Arson Analysis = identification of petroleum distillates and other

accelerants by class

--Controlled Substances = examination of powders, liquids, and plant

material for drugs


a) alcohol levels in blood and urine

b) alcohol levels in breath (using Draeger breath instruments)

c) drug (cocaine, amphetamines, PCP, opiates) levels in blood and urine

--Computer Evidence = recovery of files and/or deleted information


a) color and black-and-white film processing

b) poster-size enlargements

c) digital imaging