 Well, thank you to everyone for joining us. This is a slightly unusual circumstance and the sort of life that we're all getting used to, but of course the advantage of it I think is that we actually can attract more people from further afield than we might otherwise have. I'm particularly grateful to Martin for coordinating this. I'm currently the acting chair of the Cambridge social legal group, so I didn't think it was appropriate for me to actually be chairing the meeting as well while I try to give a seminar. So thank you very much to him for that. We've agreed that I'm going to speak for about 40 minutes after which there will be time for questions. I should say that this is very much a work in progress. I do have a written paper and I'll share my email address in the chat later on. Unfortunately, the paper is under review with a journal that imposes strict limits on being able to post things online while it's in review, so I wasn't able to share it more publicly, but I'm happy to send you a copy. The other thing to say of course is that I'm very conscious that in a mixed audience it's entirely possible that I will have completely misunderstood the science and will be taken apart in question that I suppose that's the risk to which I've exposed myself. So if Martin can concentrate on admitting people as they turn up, I'll then be able to start actually speaking. So the chimera of parenthood. I'm sorry that I don't have a handout that's available to you. I did prepare one, but we have trouble with sharing the file, but I'm hoping that I put enough effort to destruct during the talk that you'll be able to follow it nevertheless, but we can get to that in question. So in 2015 the independent newspaper reported the case of man who'd failed a paternity test in the US because it eventually transpired the genetic material in his saliva was different from that in his sperm. That was said to be the first reported instance of a paternity test being fooled by what's known as a human chimera Such a chimera has extra genes in this instance apparently absorbed from a twin lost in early pregnancy. The result was that the true genetic father of the child in question was the man's twin who'd never been born. Now the man and the child's mother in this instance were not in dispute as the paternity and parenthood on the facts of the case, but instances of chimerism nevertheless potentially present a challenge to legal systems where there is such a dispute given their frequent emphasis on genetics in determining parenthood and that's the subject of today's seminar. I want to start by exploring the phenomenon of chimerism with reference to the relevant scientific literature. Then I'll analyze the practical response of the law of England and Wales to the situation of a potential chimera or at least the likely response. The focus will be on situations where the putative father is a possible chimeric person in the context of a paternity dispute. Finally I'll consider what the phenomenon of the chimera might tell us about our understanding of parenthood and the differences between biological motherhood and fatherhood respectively. I'll draw conclusions on whether that understanding as reflected in the law and its procedures is appropriate advocating the recognition of the chimeric person as the true legal father but pointing out that this may require fatherhood to be understood as more of a process than is often realized. So first of all looking at the science. The first recorded literary reference to a chimera is in Homer's Iliad where the term is used to describe a mythical creature that is part lion, part serpent, and part goat. In medical science chimerism describes a phenomenon where an individual carries more than one complete genome. A congenital chimera is an individual who carries the cell population of dizygotic twins, a term that's usually used to describe fraternal or non-identical twins who come from separate uva and are fertilized by separate sperm. Chimerism is believed to occur because of the fusion of twins at the earliest stage of embryo development or from maternal fetal exchanges during pregnancy. Although acquired chimerism can occur as a result of blood transfusion or organ transplant. Now it's been said that chimerism is becoming well known among the general population due to its increased media presence but its presence in humans is also thought to be underestimated with most instances remaining undiagnosed because of the absence of physical symptoms and limitations of ordinary testing methods. Booklage claims that the fraction of the population who are chimeric might be as high as 10% or more and that conservatively estimated at least one live birth in eight is a product of a twin conception, the majority of which bring with them to delivery neither a coup twin nor any overt evidence of their twin history. It's also expected to become more prevalent in the light of the increased use of assisted reproduction. Now significantly for my purposes today any tissue sample from a chimeric individual may contain one or both cell populations. Some commentators have attempted to distinguish between different types of chimerism and argue that only some present difficulties for legal system. Sheets and wenk however emphasize that mixed cells of all chimeras including transplant chimeras carry DNA of four gametes. Difficulties will arise in the context of forensic or paternity testing if only one population of cells is identified from a test and it's not the pertinent one. The tissues sampled from the chimera may not contain both genomes or the minor population may be too small to observe in current routine heritage tests. This is true even if the difficulty is a rare one. A sheets and wenk put it relates to testing relies on the assumption that tested individuals carry one DNA profile in all tissues that are sampled and there can be situations where tests exclude the alleged father from paternity of the child and give no indication of a biological relationship between them. It's been said that current tests used by relationship testing and forensic labs have several inherent limitations that prohibit the routine identification of chimeric individuals. It's interesting that of course testing has taken on a whole new set of connotations for many of us but when I wrote this paper none of that had yet happened so I'm really talking about a different kind of testing today focusing on paternity testing. So with all of this in mind I want to consider English law relating to parenthood and paternity testing speculating on how it might respond to the phenomenon of the chimera. So looking now at the legal response the possibility of chimerism presents a challenge to the legal system and raises questions about what is being or should be asserted in a paternity case. So it's first necessary particularly for the benefit of those of you who aren't lawyers or aren't English lawyers to summarize the general approach to parenthood and to testing in English law before I then analyze its response to paternity and how it might cope or not with chimerism. At this stage I should emphasize that while many substantive aspects of raising a child can be determined through the exercise of parental responsibility which can be held by non-parents, parenthood per se is still both legally unsymbolically significant. For example legal parenthood remains important albeit not conclusive in the allocation of parental responsibility and liability for child support and it also determines basic entitlement in cases of intestacy so when someone died without a will. Now in England and Wales it's still the case that a child is limited to two legal parents. In English law as Lord Simon put it in the Amtel period case motherhood although a legal relationship is based on a fact being proved demonstrably by protrusion i.e the act of giving birth to a child. A child's legal mother is defined in the Human Fertilization and Embryology Act 2008 which essentially applies to assisted reproduction as the woman who is carrying or has carried a child as a result of the placing in her of an embryo or of sperm and eggs. The basic position that the birth giver is the mother thus applies even where the child was conceived using an egg that was donated or didn't otherwise belong to the mother such that the mother in those instances is not genetically related to the child. Also applies in the first instance even if it's later varied by a parental order giving effect to a surrogacy arrangement or adoption. In the recent TT case about which many of you will have heard it was held that the definition of a mother as a person whose egg is inseminated in their womb and who then becomes pregnant and gives birth to a child applies even to someone who gave birth after changing his legal gender to male. An appeal by that man was recently dismissed by the Court of Appeal albeit that it focused on statutory interpretation of the gender recognition legislation. Motherhood is thus conferred by the biological process of parturition whether it's defined a common law or by statute in the particular circumstances although it can alternatively be determined by the legal process of adoption or a parental order if one of those happened afterward. Being a mother is the status afforded to a person who undergoes the physical and biological process of carrying a pregnancy and giving birth. I'll come back to this later but it's worth emphasizing at this stage that it doesn't rely on a genetic link per se such that chimerism potentially causes fewer problems in the context of motherhood. As Schietzenwenk put it non-maternity is rarely suspected in any event. If you've seen someone give birth to a child or someone has seen someone give birth to a child perhaps there's not quite so much reason for suspicion. Paternity or non-paternity is maybe easier to hide or dispute unless and until a genetic test is performed but DNA testing of mothers is nevertheless used in England and Wales in the context of establishing both motherhood and fatherhood. Moreover the US case of fair child demonstrates that a chimeric mother could face allegations of unsavouriness where she's shown not to be genetically related to the child and cannot provide a satisfactory explanation such as egg donation or adoption for her continued claim to legal motherhood. In that case DNA testing concerning paternity indicated that Ms Fairchild was not biologically related to her children. She was therefore denied public assistance and accused of defrauding the government with the children placed in foster care despite evidence from her obstetrician that she had indeed given birth to them. During the investigation she gave birth to a fourth child in front of a court appointed witness but DNA evidence suggested she was not related to that child either. So really an extraordinary course of events. Eventually her lawyer having heard of a chimerism case requested further DNA testing of herself and her extended family. The children's DNA was consistent with that of their putative maternal grandmother and a cervical smear ultimately showed the genetic link between the children and Ms Fairchild that skin hair and saliva samples didn't. I'll consider further how an English court might respond to possible chimerism in the context of paternity once I've outlined the general approach to fatherhood. The question of a child's legal fatherhood is a bit more complex than motherhood and depends on whether assisted reproduction has been used. As with motherhood the initial determination of legal fatherhood can be buried by an adoption or parental order. Unlike motherhood or ever outside those exceptions and the context of assisted reproduction legal fatherhood concerns genetics and the provision of sperm which results in the birth of a child according to rebate parentage. The assumption being that the child has been produced by an egg fertilized by sperm containing the father's genetic material. It's this assumption that's potentially challenged by the phenomenon of the chimerism. Chimerism are not, however. Matters are not quite so straightforward as they may first appear. There remains a presumption at common law, the paterest presumption or presumption of so-called legitimacy, that a child born to or conceived by a woman during her marriage to a man is also the natural child of her spouse which has recently been extended to a child born to a woman during her civil partnership with a man. Absent adoption surrogacy or assisted reproduction that presumption of natural parenthood will also presumptively determine legal parenthood albeit that the presumption may be rebutted by evidence on the balance of probability and its value has been questioned in the modern era when DNA testing is so widely available. Where the mother is unmarried no paterest presumption obviously can exist in the same way but registration of the father on the birth certificate is considered good prima facie evidence of paternity albeit that the mother isn't even prima facie obliged to register the father as such. It's in the context of disputed parentage and paternity and consequently legal parenthood except in special cases of fathers that chimerism may cause difficulty for English family law. Leaving aside the special case of assisted reproduction for the moment the court may make a declaration of parentage under the Family Law Act 1986 and under section 20 of the Family Law Reform Act 1969 the court has the power in certain circumstances to give a direction for the use of scientific tests to ascertain whether such tests show that a party to the proceedings is or is not the father or mother of that person and for the taking of bodily samples from all or any of that person any person who's alleged to be the father or mother and any other party to the proceedings so the court certainly has powers to direct scientific testing but chimerism raises a huge number of issues and questions for such tests some of which are pertinent to the right to respect for family life under article eight of the ESA talk. Unfortunately I have time only to list them at the moment but I can go into them in greater detail in the question. First the focus of practice is currently on bucle swabs capturing cheek cells which are often insufficient to detect chimerism. Would a court be prepared to order more invasive tests and would it be sufficiently aware of the limitations of traditional DNA evidence to do so? Secondly would there be sufficient awareness of chimerism and the phenomenon amongst the legal profession to ask for such more onerous tests and could a court be persuaded not to attach undue significance to a negative finding that someone is apparently not the father? Thirdly how would the court balance the need for certainty and accuracy in relation to previous findings where evidence of chimerism is later presented? Fourthly how should a court approach the drawing of adverse inferences in the context of a refusal by a putative father to undergo onerous testing? Fifthly would the importance generally attach to truth in deciding whether to direct tests on a minor child apply in the same way in the context of chimerism? Sixthly would the possible existence of chimerism provide an additional reason to order tests and might there even be an obligation to disclose chimerism to a child because of its consequences for genetically inherited conditions? Seventhly might there alternatively be a need for caution in light of the difficulties in accepting and understanding chimerism that some children may experience? Eighthly would or should a court be prepared to order testing of the wider family which may be necessary to establish chimerism? As I hopefully make clear in the written paper which as I say I'm happy to email, while I'm optimistic that an English court faced with this dilemma would respond in an appropriately pragmatic manner the answers to many of these questions are not at all clear. Even if chimerism is adequately detected I ever there remains the question of what exactly the truth established by such testing is. I'll return to this more philosophical question in a moment but first let me say a word about assisted reproduction. So in the context of assisted reproduction fatherhood can be determined according to the provisions of the Human Fertilization and Embryology Act 2008. These can confer legal fatherhood from the outset on a person who is known not to be the genetic father of the child produced such as where the child was conceived using donor sperm. By virtue of the act if at the time of the placing in her of the embryo or of the sperm and eggs or of her artificial insemination a woman was in a marriage or civil partnership with a man and the creation of the embryo was not brought about with the sperm of the other party to the marriage or civil partnership. Essentially the mother's husband or civil partner will be still considered the father of the child unless he didn't relatively consent. If the mother isn't married or in a civil partnership with the intended father fatherhood can be conferred by virtue of the agreed fatherhood condition being met in broadly equivalent circumstances. But those are more bureaucratic because of the extra complications caused by the absence of a marriage. Where these sections apply it might be irrelevant in the context of a paternity dispute to assert that the currently recognized father is not the genetic parent of the child in a sense we already knew that he wasn't the genetic parent that was the point. This means that chimerism will cause less of a problem in some situations where the Human Fertilization and Embryology Act apply. That said there will be some situations where sperm from the intended father was to be used to make him the biological father in the context of assisted reproduction and chimerism may well wrongly suggest that an error has been made by the fertility clinic. Unfortunately the potential for the assisted reproduction provisions to assist chimeras maybe by coincidence won't be much consolation to chimeric persons who become involved in paternity disputes after conceiving a child naturally. I can go into further detail on the difficulties with assisted reproduction in this context in the questions. But it should by now be clear that the phenomenon of the chimeric raises significant practical issues in the context of paternity disputes. Even on the assumption that these issues can be pragmatically resolved by the English legal system such that a chimeric putative parent chimeric putative parent can be accurately identified chimerism gives rise to some rather more philosophical questions. I now want to canvas these non-conclusively very much so and I'd be very interested to hear your thoughts. So the phenomenon highlights the differences between understandings of different types of parenthood in English law. Motherhood is determined by the process of giving birth irrespective of any genetic link albeit that obviously in most cases the genetic link will be present. And again that's true at the outset even if the position is later varied by a parental order giving effect to a surrogacy arrangement or adoption. Outside the context of assisted reproduction and again subject to a parental or adoption by contrast the orthodox position seems to be that fatherhood is determined not primarily through a process but through a genetic link. Even in the current law of surrogacy genetics remain key. One of the applicants for a parental order must be the genetic parent of a child such that only the longer and more arduous route of adoption is available to those who are not albeit that in this particular instance the relevant genetic link can be provided by the mother as an alternative to the father. The challenge issued by chimerism is that arguably the true father of the child can be the sibling of the person who ejaculated to produce the sperm with which the mother was inseminated. It's already legally possible for a child only ever to have had one parent in English law and of course many children will know only one parent as a matter of practical reality. But there's arguably little to be gained by asserting that a child's father was someone who never became a legal person simply because we've decided to attach significance to a particular aspect of biology. That's not withstanding the strong case that can generally be made for regarding genetics as a core part of identity. Quite apart from the potential emotional implications of being unexpectedly rendered fatherless because of a quirk of biology significant substantive disadvantages for the child concern would flow from the conclusion that the true genetic and therefore legal parent of a child is someone who never himself became a legal person. These would include a presumptive deprivation of inheritance rights in cases of intensity and child support and the chimeric person's ability to care for the child may be rendered precarious in contrast to the parent's presumptive right of parental involvement now enshrined in statute. There is the possibility that some such difficulties could be resolved through mechanisms such as adoption, the granting of parental responsibility or related orders to the non-parent, the writing of the will, or the recognition of the child in question as a child of the family who has some potential claim to financial support. Sorry, I'm having technical problems. But the problem is that all of these things would be mechanisms that may not be used when problems come about and disputes come about. So there are various problems with the possibility of denying parenthood to the chimeric person. And a solution may be costly in financial and emotional terms. Now, again, many children deal with similar issues in practice without being bothered by a chimeric person. And the absence of inheritance rights for one child, for example, could increase the entitlements of those fortunate enough to have been conceived in circumstances that they are recognised as legal children. But it's not necessarily desirable for English law to deny fatherhood where there is, to put it mildly, one highly plausible candidate, i.e., the chimeric father, and one candidate who was never himself born. Admittedly, there is precedent in England and Wales for a person whose life didn't overlap with the child's conception. Being symbolically recognised as the father, specific provision is made for posthumously conceived or implanted children to have a now-deceased person recognised as their father if he valiantly and formally consented to that recognition. But in such circumstances, the pre-deceasing father did become a legal person, and the symbolic recognition of his status doesn't, unlike in a chimerism scenario, presumptively deprive the child of another parent in the same way. And there are various issues and contrasts that can be made with that situation, which I can go into again in the question. So I think we kind of know what answer we want to come up with, and the question is, how do we get there? So on what basis can it be suggested that the chimeric person himself is the true father of the child concerned, which is the conclusion that's likely to be desirable, as well as the one that will probably be drawn as a matter of pragmatism? For present purposes, I'm posing this question within the broad framework of current English law, leaving aside for the moment the possibility that purely social parenthood might be substantively recognized after birth. One solution would simply be to assert that the chimeric doesn't own all of his genetic material, notwithstanding the fact that some of it, sorry, does own all of his genetic material, notwithstanding the fact that some of it derived from his unborn sibling. So he's saying, well, the genetic material was used by him, and it's all his. On this analysis, the chimeric person genuinely has two sets of genetic material, being himself genetically tetrapalentum, as Martin himself puts it, and that would be reflected in different proportions throughout the cell. But as would eventually be confirmed by one of the tests considered earlier, one of those sets of DNA would be validly recognized as having produced the relevant child. A possible objection to this would be that it undermines the dignity of the unborn sibling, who did have a complete and unique set of DNA that happened to be absorbed by his sibling before being used to produce the eventual child. Many would no doubt counter that any such question of dignity is resolved subject to limited protection within abortion, human tissue, and other legislation, by the denial of more general legal personhood to that sibling, because he'd never been born. But it's arguable that this view adopts a particular and potentially artificial understanding of biology's implications that's not necessarily inevitable. Another way of resolving the matter in favor of the chimeric person being the father would be to suggest that English law's understanding of fatherhood is or at least should be subtly different from what is tended to be thought. This would apply outside the context of assisted reproduction within the scope of the Human Fertilization and Embryology Act. It would also be subject to later variation through adoption or parental order in the usual way. This principle would be that fatherhood is based on a process after all, that of semen derived from one's body being used to impregnate the mother, a potential application of what Martin again has described as the coital aspect of parenthood. This would apply irrespective of the genetic content of that semen, such that the difficulties raised by chimerism would be at least very considerably reduced. And it also is, in my view, consistent with other aspects of the English law of paternity. Could it be argued that the genetic link usually determined by testing serves or at least should serve as a proxy for insemination by the putative father rather than the other way around? It might reduce the value of genetic testing, but as I've already highlighted, that value is already reduced to some extent in this context anyway. An advantage of the approach would be, in fact, that it reduces the differences between the bases on which legal motherhood and fatherhood respectively are conferred. Very significant differences would inevitably remain between ejaculation and insemination, on the one hand, and pregnancy and parturition on the other. And Lady Hale attached particular significance to the gestational bond between mother and child in the House of Lords in Rigi Children Residence St. Sext's partner. But both motherhood and fatherhood would, in the first instance, flow from processes surrounding the child's conception and birth rather than genetics per se, in a context where the wisdom of the differences between the statuses of motherhood and fatherhood is increasingly being questioned in any event. I have to concede, however, that this second approach might be considered by many to be unnecessary, and that by far the simplest solution is to regard all the genetic material contained within the chimeric person as relevantly his, notwithstanding the fact that it ultimately derived from his twin who never had the privilege of being born. I'm conscious that I've thrown a lot of detail at you, but I hope that I can expand on things in the questions. What can I say by way of conclusion? Well, English law's response to suspected chimerism is not necessarily clear. It's to be hooped that the possibility that the putative father is a chimeric person will be appropriately recognised and investigated where a DNA test is failed, particularly as an alternative to attaching undue significance to a negative finding alone. It seems likely that a judge in England and Wales would respond pragmatically to the situation and order or at least accept evidence from a more thorough range of tests than those usually undertaken. The issues are complicated, however, by the fact that father's motivations may vary in the context of paternity disputes. Some may wish to establish paternity as a prerequisite to gaining parental responsibility, presumptive involvement in the child's life or perhaps even inheritance rights. Others will be seeking to negate paternity and thus legal fatherhood so that they can in turn avoid financial liability for the relevant child. The drawing of adverse inferences from a refusal to undergo a more onerous series of tests in a case of suspected chimerism raises difficult issues even if the tests are still non-invasive. More broadly, I've highlighted some issues of principle raised by chimerism, including the differences between motherhood and fatherhood as they're currently understood and constructed by English law. Outside the context of assisted reproduction, surrogacy and adoption, the orthodox understanding is that motherhood is conferred by a process of giving birth while fatherhood is ultimately based on genetics. Chimerism potentially challenges the latter assumption since the genetic material ostensibly contributed by the chimeric father may have derived from the chimeric sibling, albeit that the sibling never straightforwardly became a legal person. It may be that the conceptual difficulty can be straightforwardly resolved through the simple assertion that the genetic material belongs to the chimeric person, whether it derives from him in the expected way or ultimately from his unborn sibling. But the alternative might be that chimerism means that the notion of paternity, again outside the assisted reproduction context, ought to be regarded as more of a process after all based on the insemination of the mother. So thank you for listening, I'll leave it there, and I'm very happy to take questions. And Martyn, are you happy to share the discussion or would you like me to carry on? I can help a little bit. So why doesn't everybody initially unmute themselves and show their appreciation by clapping loudly, or you can display your hands in the reactions button at the bottom of your screen? So hopefully you can hear that. First virtual round of applause.