| |
This
Article has been reprinted with permission and is an excerpted
Chapter from a Web Edition book Copyrighted by the
Genelex Corporation. No
reprints are permissible except as allowed by the
Genelex Corporation.
Genelex Paternity and Forensic DNA Testing Laboratory is an
internationally recognized leader in paternity and forensic DNA
analysis.
Introduction to Parentage Testing.
In the United
States, establishing paternity has become a major industry.
Government efforts to recover child support funds bring in over
five billion dollars a year at a cost of one-and-a-half billion
dollars. State and local child support agencies, working under
Title IVD of the federal Social Security Act, Aid to Families
with Dependent Children, administer these programs for the
benefit of unsupported children. This statute requires that when
a woman obtains public assistance for her children, she MUST
name the possible fathers. These programs generate the bulk of
more than 220,000 paternity tests performed annually. In a
country where 30% of births are to single mothers, and 15% of
fathers of record are not the biological father, the large
number of tests is not surprising.
Parentage testing cases are numerically
the largest user of DNA testing. More than 200,000 of the
paternity tests performed in the United States every year use
DNA testing exclusively or as a supplement to conventional blood
testing. HLA (Human Leukocyte Antigen) and other classical blood
typing tests often can resolve a routine paternity case without
resorting to DNA testing. The HLA blood types are the types that
must be matched before an organ transplant, such as bone marrow,
kidney or heart, can succeed. Limitations of conventional blood
testing are that the blood must be fresh when tested, and only a
limited amount of genetic information is obtainable. Also
non-blood cell types, such as those found in semen, do not have
an HLA and most other common blood types, rendering this type of
testing much less useful in forensic cases. The advantage of DNA
testing is that many more variable genes, up to thirty or more,
are available. In effect, our ability to do paternity testing is
no longer limited by the amount of genetic information that we
are able to obtain.
Most paternity testing is done for
financial reasons, i.e., to establish legal responsibility and
provide for child support. Even more important are the emotional
and social issues. When testing can demonstrate conclusively to
a man that he is the father of a child, then he is more likely
to provide not only financial support, but emotional support as
well. He may bond with the child and take an active part in its
life. The importance of establishing paternity early is nowhere
more clearly shown than in the testing of adult children, some
of whom are in middle age. "Who is my father?" is a question
that may have haunted them their entire lives.
It wasn't very long ago that obtaining a
paternity test was an uncertain, expensive and inconvenient
process. It was hard to find a place to have the blood drawn to
initiate the testing and redraws were common as the blood had to
reach the laboratory in one or two days. A doctor's or a
lawyer's involvement might have been required, and, even after
the effort and expense, the results often came back with a
considerable degree of uncertainty. Also, there were no
inspection and certification programs available to parentage
testing laboratories which provide an assurance of quality.
DNA testing has made the process
convenient and the results conclusive. The testing is still
expensive and takes a week or two to complete, but anyone can
order it. In all but the rarest of instances, the DNA test
results provide a level of certainty so high that paternity
will, for all practical purposes, be proven or disproved.
One of the greatest benefits DNA has
brought to parentage testing is the ability to solve many more
types of cases. In the usual case, tests include all three
parties, i.e., the mother, child and alleged father. With DNA,
it is not necessary to have the mother's sample in order to
provide a conclusive test result. It is possible to distinguish
between two brothers provided they are not identical twins. In
many cases, it is possible to perform the DNA tests when the
alleged father is deceased or otherwise unavailable. It also is
possible, using DNA, to perform testing before or at the time of
birth. Tests also can be performed on some very unusual samples
such as envelope flaps, cigarette butts, and very old blood
stains.
What Happens at the Sample Collection
Throughout this country, and the entire
world, is a network of individuals licensed and experienced in
the legal sample collections that are necessary in paternity
testing. These collections differ from medical collections by
the extent to which they are documented. Clients who are being
tested for paternity will be asked to show a picture ID, fill
out and sign release forms and identification labels, and a
photo or thumbprint will be taken. In this way the chain of
custody (COC) that must be maintained throughout the transport
and testing can be assured. In order for the COC to have maximum
integrity the tested parties should not be involved in the
shipping or handling of the transport kit. It should be sent
directly to the collection site or personal physician, and
include pre-addressed return airbills with instructions.
Only a small volume of blood, a teaspoon
or less, will be taken in a draw. Children, even babies, usually
tolerate it quite well. The blood samples from babies also are
drawn from the arm because it is less painful and much quicker
than a heel or finger stick. Unlike former practices, blood now
can be drawn any day of the week, and all parties need not be
drawn at the same time or place.
Buccal or Cheek Swabs and Home DNA Paternity
Tests
More and more collections are performed
using a "buccal swab," a Q-tip that has been rubbed on the
inside of the cheek. This type of collection has made the "home
paternity DNA test" possible. The home test is the ultimate in
convenience. Unfortunately, it has minimal legal standing
because it is generally impossible to independantly verify the
identity of the individuals who have been tested. There is no
chain of custody. Another type of home DNA test overcomes these
obstacles because the collection is performed in home by a
medical professional who comes to the home. This level of
service is not available everywhere but is becoming more
available all the time.
PARENTAGE TESTING APPLICATIONS
Prenatal and Newborn
Paternity Testing
Formerly, it was impossible to test babies
until they were six months old. Testing blood from the umbilical
cord of a newborn now is one of the most convenient and
effective ways to obtain a paternity test. At the time of birth
labor and delivery staff will take blood from the umbilical cord
after the baby is born, collect from the mother and ship the
samples to the laboratory. Arrangements must be made in advance
and if the alleged father has been drawn prior to the birth,
testing can start immediately.
One of the fastest growing areas DNA
paternity tests is prenatal testing. While it has been possible
for many years to perform a prenatal test for paternity, it has
not been routinely done because of the small risk to the fetus
and the long turn around time (six to eight weeks.) That is
changing as the amniocentesis and chorionic villus sampling
procedures become more accepted and routine. These are the
procedures for obtaining cells from the unborn baby which, in
the past, have been limited to women over thirty-five or for
families with a history of genetic disease. With the latest in
DNA testing methods results can be obtained in a matter of days.
Deceased Alleged
Father
This type of DNA testing often is needed
to obtain Social Security or insurance benefits, to settle an
inheritance dispute or to establish standing in a wrongful death
action. There are two basic approaches to solving these cases.
The first is to obtain a postmortem sample of the father's DNA.
The second is to reconstruct his genotype based on surviving
family members. Samples from the deceased may be obtained from
the medical examiner, coroner or other pathologist who may have
performed an autopsy, an associated toxicology or medical lab,
the funeral home before or after embalming, or even following
burial for up to several years.
Kinship Analysis
- Missing Alleged Father
If samples from the deceased are not
readily available then the alleged father's genotype can be
reconstructed by testing close relatives. The most
straightforward of these tests is a grandpaternity test in which
the alleged father's parents are tested. If one or both of his
parents are missing, then samples from his siblings or other
children can be used and extended typing performed. Any
combination of three or four of these close relatives will
result in a highly conclusive test. When fewer relatives are
available for testing, the ability to provide a conclusive
result decreases. Relatives farther removed from the alleged
father such as cousins are not related closely enough to provide
useful information. One caution to this type of testing is that
if the relationships are misrepresented to the laboratory, a
false negative may result.
Sibship
Analysis
The most difficult kinship analysis is to
determine if two individuals are full or half siblings when
those individuals are the only ones available for DNA testing.
If the number of tested siblings increases or other relatives
become available, the degree of certainty increases
dramatically. It also is easier to determine if two individuals
are full siblings or completely unrelated. Advanced genetic
methods and specialized computer programs are required to
reliably solve these cases. It may be necessary to test twelve
or fifteen or more genes in order to make a determination.
The most common and most disturbing
criminal paternity cases are those involving the sexual abuse of
a child. Laboratory testing is not possible in many of these
cases because the abuser is a relative or close friend of the
family, and the crime comes to light after the physical evidence
is gone. Sometimes these unlawful sexual contacts do result in a
pregnancy, especially if they continue over an extended period
of time. In this instance, the DNA testing is usually routine
and can be performed on the child or an abortus that is older
than six weeks. DNA testing may be especially useful if there
are closely related suspects, such as a father and son or two
brothers. Criminal cases also may require the application of
non-routine statistical and reporting techniques depending on
the requirements of the court.
Cases where the victim of sexual abuse is
underage rarely go to court. The offender usually will receive a
lower prison term if he pleads guilty. Conviction in the face of
DNA evidence is almost inevitable. In cases where the victim is
an adult and consent is a defense, the defendant may change his
story when he realizes that the DNA testing results are almost
impossible to refute. The jury is usually unaware of this change
of story and so often will vote to acquit the defendant.
DNA parentage testing has been questioned
by the courts in only a handful of cases. Typically, less than 1
or 2 percent of civil cases result in a case contested in trial.
The opportunity to have testing repeated by the same or another
laboratory usually can settle most disputes to the satisfaction
of all tested parties. In criminal cases, when the testing is
scrutinized extensively in court, it is almost universally
accepted.
Genetic
Reconstruction or Reverse Paternity
These techniques often are used in
homicide investigations. Suppose that there is a tissue sample
from an unidentified deceased individual, or a stain from a
crime scene and investigators have an idea of who may be the
sample's source. If the decedent's parents or children are
available, it will be possible to compare the related survivors'
DNA profiles with that of the deceased to conclusively determine
whom the remains came from.
Test Results
Paternity testing is possible because
everyone has two copies of their genetic information, half from
each of the parents. If a child has a gene that didn't come from
the mother, then it must have come from that child's biological
father. If the alleged father does not have that gene, the
obligate gene as it is called, then he cannot possibly be the
father. He is excluded from the group of men who could be the
father of the child. There is one exception. If a mutation has
occurred, which means the gene changed when it was passed from
the father to the child. These mutations rarely occur, but they
occur often enough that statistical methods are available for
dealing with them and two DNA exclusions are required before
reporting out a DNA paternity test result.
The other possible outcome is that the
alleged father has the obligate gene and so is included in the
group of men who could be the father of the child. In effect,
what paternity testing does is examine a series of genes until
the group of men who could be the father of the child is
narrowed down to the point that we can, for all practical
purposes, be certain that he is the father. In DNA testing, this
can be accomplished by testing as few as three highly variable
genes.
Two different ways are used to report the
two possible testing outcomes. An exclusion is reported as a
simple statement that the alleged father is excluded from the
group of men who could be the father. In the case of an
inclusion, a statistical analysis is performed based on how
common or rare are the obligate genes. These are the genes that
the alleged father could have contributed to the child and that
must have come from the child's biological father. The
inclusionary results are expressed in the following two ways:
The Paternity
Index
The first is the paternity index (PI),
which is a simple odds ratio. Because of the increased accuracy
possible with DNA testing, the generally accepted minimum
standard for an inclusionary result has risen to a PI of 100.
This means that the alleged father has a 99 to 1 better chance
of being the father than a random man. It does not mean that the
test is only 99 percent accurate. A more realistic way to look
at this result is to consider that the alleged father has a PI
of 100 and that the genetic profile he must donate is found in
approximately 1 in 100 randomly chosen men. If he has been
falsely accused, then he has the required 1 in 100 profile. The
probability of these two events occurring together is more
realistically thought of as 1 in 10,000.
DNA test results typically produce odds
ratios of hundreds or thousands to one. As a practical matter,
once a PI of 100 is reached, the probability of overturning that
result with further testing becomes extremely small. In
practice, the test results are reported out according to the
race of the alleged father. While the results can vary slightly
from race to race, as a practical matter, when modern DNA
testing methods are used, the race of the father doesn't make a
significant difference.
Probability of
Paternity
In the second way, the probability of
paternity is calculated simply by converting the PI to a
percentage. However, it can be the most confusing because the
equation that is used for the calculation contains a term called
the "prior probability." This term takes into account the
non-genetic factors that would have a bearing on paternity. In
the laboratory a neutral value of 0.5 is universally used. It
favors neither the alleged father nor the mother.
The paternity index and probability of
paternity represent a comparison of the alleged father against a
random man in the population. If there is a close relative who
also could be the father he also should be tested. If he is
unavailable, then the laboratory can take that fact into account
when doing the testing and calculations.
Choosing a
Laboratory
Because paternity laboratory inspection is
not mandatory, there is a wide range of quality among the
laboratories. On the fringe are a number of small laboratories
which do a low volume of testing and do not subscribe to the
established quality control assurance programs. In evaluating a
parentage testing laboratory, one should ask if it is accredited
in DNA testing by the American Association of Blood Banks. Labs
may be accredited in the older types of testing, such as HLA and
red blood cell testing, but not in DNA testing.
When contacting a laboratory, if it is not
possible to talk with an understanding, helpful and
knowledgeable client services representative, it might be
advisable to look elsewhere. A lab may do fine work, but if
there is not someone available to clearly explain the process
and results, it can be frustrating. Another factor which can
help in laboratory selection is whether or not the laboratory
has provided testing and testimony in criminal cases, which
require the most advanced expertise.
|
|
Call (612) 240.8005
Wisconsin Divorce
Wisconsin Divorce Issues
Minnesota Divorce
Minnesota Divorce Issues 
ASK-A-LAWYER questions
Ask-A-Lawyer your legal question
Family Law Articles
Review legal articles
Divorce Bulletin Board
Ask a question or review postings on our Family Law Bulletin
Board
Divorce Forms
A comprehensive listing of divorce and divorce related forms for
all states
Divorce Book
Store
Review Books on Winning Custody, Child Support, Property
Divorce
Links
Review links to Divorce and Family Law Resources including Men's
and Women's Rights
Glossary
of Divorce Terms
from DivorceChoice.com
|
