Law, ethics and medicine
The case for re-thinking incest laws
C Farrelly
ABSTRACT
The recent case of German siblings Patrick Stübing (age
30 years) and his sister Susan Karolewski (age 22 years)
has reignited debate over the criminalisation of sexual
intercourse among consanguine descendants. The primary
justification for criminalising incest is the purported
increased risk of genetic disabilities among offspring, but
is criminalising sexual intercourse an empirically sound
and proportionate response to this increased risk? To
answer this question we must consider the specifics of
the harm in question (eg, is it a harm to the child or a
societal harm) and the magnitude of the harms of the
intervention. The example of incest law has important
implications for liberal societies. If we can justify
imprisoning consenting adults for choosing partners who
will increase the risk of having children with disabilities,
then we set a troubling precedent for all couples who may
pass on genetic disorders to their children.
Imagine the following scenario: Patrick and Susan
are consenting adults who are in love with each
other. They decide to start a family. However,
recent advances in our understanding of human
genetics give us reason to believe that this
particular couple will have an increased risk of
having a child with a disease or disability. For
example, if Patrick has been diagnosed with
Huntington’s disease, a late-onset neurological
disorder, then there is a 50% chance that any child
he fathers would also be born with this disorder.
Alternatively, if Patrick and Susan are both carriers
of the cystic fibrosis gene then there is a 25%
chance that any child they have will be born with
cystic fibrosis, a genetic disorder that can reduce
life expectancy by more than 50%.
Suppose now that law-makers decided that the
increased risk of disease in this case was intolerable.
So intolerable that the government has threatened
to imprison Patrick and Susan if they are together.
The justification given for such a stringent,
intrusive intervention is that the government
wants to reduce the likelihood of children being
born with genetic abnormalities. How would we
react to this kind of scenario?
The case of Patrick and Susan is not a fictional
one, nor is the example of the intrusive state
intervention I mentioned something taken from
the history books of past eugenic policies. In the
real life case of Patrick and Susan neither carries the
gene for Huntington’s disease or cystic fibrosis, but
their offspring do face an increased risk of disability
and this risk stems from the fact that Patrick and
Susan are siblings.
Incest has long been a social taboo in many parts
of the world. The recent case of German siblings
Patrick Stübing (age 30 years) and his sister Susan
Karolewski (age 22 years) has reignited debate over
the criminalisation of sexual intercourse among
consanguine descendants. The couple have four
children and Patrick Stübing has already spent
2 years in prison. On 13 March 2008 Germany’s
constitutional court rejected Patrick Stübing’s
request that section 173 of Germany’s Criminal
Code be invalidated. This section of the Criminal
Code covers ‘‘sexual intercourse between relatives’’
and section 1 states, ‘‘whoever completes an act of
sexual intercourse with a consanguine descendant
shall be punished with imprisonment for not more
than three years or a fine’’.
The primary justification for criminalising incest
is the purported increased risk of genetic disabilities
among offspring, but is criminalising sexual intercourse an empirically sound and proportionate
response to this increased risk? To answer this
question we must consider the specifics of the
harm in question (eg, is it a harm to the child or a
societal harm) and the magnitude of the harms of
the intervention.
With respect to the harm of incest (when the
sexual relations occur among consenting adults),
the most commonly identified harm is the
increased risk of genetic disabilities among offspring. It is important, however, to distinguish
between the purported harm to the children
themselves and the purported harm that a population could experience from a decline in genetic
diversity brought about by inbreeding en masse.
Neither of these purported harms justify the
intrusive and severe punishment that section 173
of the German Criminal Code sanctions. Indeed,
incest laws are best viewed as a legacy of the illinformed and unfair eugenic practices of the past,
and to reaffirm the validity of such laws is
particularly dangerous given the advances that
are being made with respect to genetic testing for
disease and disability.
Whatever one might say about the harms of
incest, it cannot be said to harm the children that
are born from an incestuous relationship. This is so
because the only alternative for these children
would have been non-existence. Assuming the
disability in question is not so severe that these
children would not have a life worth living, we
cannot say that their parents’ actions have harmed
them in some way. For their parent’s actions result
in their existing in the first place.
The other obvious harm to consider is the ‘‘third
party’’ societal harm that could result from
permitting inbreeding. Widespread practices of
inbreeding could threaten genetic diversity and
thus lead to an increase in genetic disease and
abnormalities, which could in turn place significant
pressures on scarce medical resources. In order to
make this case it would have to be true that genetic
diversity would be under serious threat if incest
J Med Ethics 2008;34:e11 (http://jme.bmj.com/cgi/content/full/34/9/e11). doi:10.1136/jme.2008.025346
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Queen’s University, Kingston,
Canada
Correspondence to:
Dr C Farrelly, University of
Waterloo, 200 University
Avenue West, Waterloo, Canada
N2L 3G1; farrelly@queensu.ca
Received 25 March 2008
Revised 25 March 2008
Accepted 16 May 2008
Law, ethics and medicine
was de-criminalised, and there is no credible empirical basis for
believing this to be the case. France and Sweden, for example,
do not have laws against incest and yet neither society has been
plagued by mass inbreeding. This suggests that less intrusive
measures (eg, social disapproval, education, genetic counselling,
etc) can be effective in terms of minimising the likelihood of
inbreeding. The government should only pursue the most
intrusive violations of reproductive freedom in those cases in
which less restrictive measures are ineffective at promoting a
very pressing and substantial aim, but incest laws are not
necessary to protect genetic diversity. The danger with lowering
the threshold for rational connection in this instance is that
whatever one takes that threshold to be, the same standards
could be used for other reproductive choices, such as parents
2 of 2
who are at risk of passing on a genetic disease or disorder
through sexual intercourse with someone who is not a family
member.
The example of incest law has important implications for
liberal societies, for the stakes go much further than our
disapproval of incest. Such laws also set a precedent for our
attitudes concerning the scope and limitations of reproductive
freedom. If we can justify imprisoning consenting adults
for choosing partners who will increase the risk of having
children with disabilities, then we set a troubling precedent
for all couples who may pass on genetic disorders to their
children.
Competing interests: None.
J Med Ethics 2008;34:e11 (http://jme.bmj.com/cgi/content/full/34/9/e11). doi:10.1136/jme.2008.025346