## 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. Related Articles • Forum •

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 paternity cases.

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," he said.

"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 problems."

Q. What exactly is a forensic mathematician?

A. 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.

In 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.

Q. 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 rich.

How did that come to happen?

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 Asian-Pacific world.

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 any home.

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 blood.

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.

Q. Software you designed has also been used in reuniting families separated by the 1970's "dirty war" in Argentina.

How does that work?

A. 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.

Q. The immigration services of several different countries have bought your software. Why?

A. 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.

When that 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.

Q. What is the most interesting thing you've learned about human beings from your work?

A. 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.

What is 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 well.

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.

Q. How did you develop this odd but interesting profession?

A. I come from a mathematical family. My father taught and my mother was an artist and a politician -- she was mayor of Palo Alto.

In my 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 mathematics.

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 money.

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 writer.

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.

Q. Is freelance mathematics lucrative?

A. It's not bad. I can do what I want, but I make less than most senior academics.

Q. 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?

A. 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.

They gave up on the strategy of disproving the DNA evidence. There obviously was a match in the blood. They never denied it.

Q. What did you think when you first heard of Monica Lewinsky's unlaundered blue dress?

A. I tried not to pay attention.

I was 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.

Q. Does your work give you satisfaction?

With this kind of work, at least you have something you can hold on to.

It's a tool that can make the system more just.

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