August 8, 2000
A CONVERSATION WITH / Dr. Charles Brenner
A Math Sleuth Whose Secret Weapon Is Statistics
By CLAUDIA DREIFUS
Peter DaSilva for The New York Times
Math whiz and rebel, Dr. Charles Brenner travels the world helping scientists analyze the data that are used in DNA investigations.
OAKLAND, Calif. -- In a time
when full-time academic appointments are hard to come by, some
mathematics Ph.D.'s may consider
the career path taken by Dr. Charles Brenner, 55, one of the world's first
fully employed freelance mathematicians.
Dr. Brenner calls himself a forensic mathematician and his business
card reads, "Charles H. Brenner,
Ph.D., Aphorisms, Inferences and
Conclusions From Thin Air."
As part of his work with his consulting company, DNA-View, Dr.
Brenner travels around the globe
helping scientists do the mathematical calculations necessary to analyze
DNA evidence. He also advises in
Dr. Brenner has always been a
math rebel. In the 1970's, a time
when he should have been finishing
his graduate studies, he went to London where he supported himself for
six years by playing bridge.
He returned to the United States in
1974 to get his doctorate in number
theory from the University of California at Los Angeles.
After completing his degree in
1984, he found that some software
consulting he had been doing over
the years seemed to evolve into new
work in mathematical consulting associated with DNA investigations.
"I like teaching as an academic
visitor," Dr. Brenner explained on a
recent afternoon while sitting in his
office in his home here.
"But, in many places, the academic environment can be stultifying,"
"So this is a wonderful alternative. I get to travel the world,
encounter different cultures, rub
shoulders with some great scientists,
and I get to look at vexing human
What exactly is a forensic mathematician?
It's a term that I invented. It has
to do with the application of mathematics in the courts. Virtually all I do
is DNA identification. The most obvious example is I work out probabilities.
If you have, for instance, genetic
material derived from the crime
scene, you have a suspect, and the
DNA matches -- the question is, Do
they match by coincidence, and if so,
how big a coincidence is it? There
are population studies that show how
common various DNA traits are.
the case of stain-matches, all I have
to do is multiply together a bunch of
probabilities in order to get an answer.
I've worked for defense lawyers
and for prosecutors.
Also, a lot of
what I do is in paternity cases.
Your consultations for a Filipino
court in the paternity-inheritance
case of the late California millionaire
Larry Hillblom made several Amerasian orphans very happy -- and
How did that come to happen?
A judge in Saipan asked me to
Hillblom had a fortune. He'd
used it to indulge his taste for sex
with young Asian women. After
Hillblom died, there were all these
young children scattered all over the
They were potential heirs because, according to
California law -- he was a Californian -- they had not been specifically
disinherited in a will.
So to prove paternity, samples of
Larry Hillblom's DNA were needed.
However, when an investigator went
to Hillblom's Asian homes, strangely
no genetic material could be found.
No hair, no tooth brushes, none of the
normal things are that are usual in
Blood samples of these children
and their mothers were then assembled.
None from Hillblom's California relatives were available for that.
The relatives wouldn't cough up any
There was a hospital in California
that had a mole of Hillblom's, but
they refused to produce it.
They subsequently produced the wrong mole.
It was all very strange.
Given it was the only possibility, I
designed a computer program to
look at the genetics of these children.
Of the DNA profiles that came to me,
most of the children proved to have a
similarity that could only be explained if they had the same father.
That, along with evidence a relationship between the mothers and Hill
blom, won the orphans a lot of money.
Software you designed has also
been used in reuniting families separated by the 1970's "dirty war" in Argentina.
How does that work?
Well, you know, in Argentina,
there are about 300 adults who were
infants in the 1970's, and whose parents were murdered by the military.
These orphans were subsequently
given to childless military families to
adopt. I've designed software, used
by the laboratory there, which helps
make genetic identifications by looking at the genes of still-living grandparents.
A couple of weeks ago, I got the
case of an eminent Uruguayan, a
Nobel laureate, named Juan Gelman.
His son and daughter-in-law
fled to Argentina from Uruguay in
the 1970's, and they were killed there
as "terrorists." Their little child was
apparently auctioned off to someone
in the military.
Through underground sources,
Gelman was eventually able to find
out what happened to his grandchild.
He was pretty sure a certain young
Argentine girl from a military family was her.
The girl already had her own suspicions because her adoptive father,
on his deathbed, said, "I hope you
can forgive me," though he didn't
say more. Gelman contacted the girl
and gradually revealed what he believed to be their kinship.
My job was to make the calculation that nailed it down. I did the
calculations and the data was overwhelming consistent that this girl
was his grandchild.
The immigration services of several different countries have bought
your software. Why?
Well, in Denmark for instance,
there is as law where if one person
has gained legal entry, then certain
relatives are allowed to immigrate,
too. Well, in Somalia, where a lot of
immigrants seem to come from,
there's a very broad definition of
"family." A potential Somali immigrant to Denmark might feel he or
she is entitled because of membership in the same clan.
happens, the Danish authorities go to
a DNA laboratory that uses my software and who I consult for, to check
the odds of a direct relationship.
What is the most interesting
thing you've learned about human
beings from your work?
That quite a bit of adultery is
intrafamily. One of the problems
that paternity labs come up with is
where a man is accused of paternity,
and upon testing, it seems that he
shares a lot of genetic similarity with
the child in question, but not enough
to be that child's father.
going on here?
In those cases, you always wonder
if the man being sued is not a father,
might he not be the uncle! An uncle
would explain this evidence very
So what we have is a woman
who is having relationships with a
husband and the husband's brother.
My colleague Jeff Morris and I did
an analysis some years ago in which
we came to the conclusion that this
kind of relationship happens in at
least 1 percent to 10 percent of cases.
How did you develop this odd but
I come from a mathematical
family. My father taught and my
mother was an artist and a politician
-- she was mayor of Palo Alto.
family, practical mathematics was
frowned on -- statisticians, we didn't
even talk of them. I find it rather
amusing that I now do very practical
But my history is this: I was in
England during the Vietnam War,
avoiding the draft, and making a
kind of living by playing bridge for
By the time the war was
over, I returned to the U.S. and graduate school, and I started developing
a career for myself as a software
The software writing led to
creating this DNA software.
It's become a full-time business -- the software, consulting, teaching.
Basically, I'm a freelance mathematician.
Is freelance mathematics lucrative?
It's not bad. I can do what I want,
but I make less than most senior
The murder case where most of
us learned about DNA evidence was
that of O. J. Simpson. How would you
rate the presentation of DNA issues
during that trial?
The defense did something very
clever from the DNA point of view:
they said the evidence was planted.
Their basic strategy was even if it
matches, it was a plant.
up on the strategy of disproving the
DNA evidence. There obviously was
a match in the blood. They never
What did you think when you first
heard of Monica Lewinsky's unlaundered blue dress?
I tried not to pay attention.
impressed by Bill Clinton's toughness in the situation, but it did strike
me that if they could get a typing, his
goose was cooked.
Does your work give you satisfaction?
Sure. We are always reading
about people who are very critical
about the justice system.
kind of work, at least you have something you can hold on to.
It's a tool
that can make the system more just.