Lucia de Berk

Lucia de Berk

Lucia de Berk. Photo: (c) Carole Edrich

Lucia de Berk (born September 22, 1961 in The Hague, Netherlands) is a Dutch nurse who was sentenced to life imprisonment in 2003 for four murders and three attempted murders of patients in her care. After an appeal, she was convicted in 2004 of seven murders and three attempts. Her conviction is controversial among the media and scientists, and has been questioned by investigative reporter Peter R. de Vries. De Berk is known as Lucy de B. or more commonly as Lucia de B. On October 7, 2008, the case was reopened by the Dutch supreme court, as new facts had been uncovered which completely undermine the previous verdicts. Lucia has been set free, and the trial is starting all over again.


<![CDATA[ // ]]>

The case of Lucia de Berk

As a result of an unexpected death of a baby (Amber) in the Juliana Children’s Hospital (JKZ) in The Hague, The Netherlands, on September 4, 2001, earlier deaths and resuscitations were scrutinized. Between September 2000 and September 2001 there appeared to have been nine incidents, which earlier had all been thought unremarkable but now were considered medically suspicious. Lucia de Berk had been on duty at the time of those incidents, responsible for patient care and delivery of medication. The hospital decided to press charges against the licensed child nurse.

Life sentence

On March 24, 2003, de Berk was sentenced by the court in The Hague to life imprisonment for the murder of four patients and for the attempted murder of three others. The verdict depended in part on a statistical calculation, according to which, allegedly, the probability is only 1 in 342 million that a nurse’s shifts would coincide with so many of the deaths and resuscitations purely by chance. De Berk was however only sentenced in cases where, according to some medical expert, other evidence was present or in which, again, according to some medical expert, no natural causes could explain the incident.

In the appeal on June 18, 2004, de Berk’s conviction for the seven murders and three attempted murders was upheld. The crimes were supposed to have taken place in three hospitals in The Hague; the Juliana Child Hospital (JKZ), the Red Cross Hospital (RKZ) and the Leyenburg Hospital where de Berk had worked earlier. In two cases the court concluded that there was proof that de Berk had poisoned the patients. Concerning the other cases the judges considered that they could not be explained medically, and that they must have been caused by Lucia de Berk, who was present on all those occasions. The idea that only weaker evidence is needed for the subsequent murders after two have been proven beyond reasonable doubt has been dubbed chain-link proof by the prosecution and adopted by the court. At the 2004 trial, besides a life sentence, de Berk also received “tbs” (“terbeschikkingstelling”, detention with coerced psychiatric treatment), though the state criminal psychological observation unit did not find any evidence of mental illness.

Important evidence at the appeal was to be the statement of a detainee in the Pieter Baan Center, a criminal psychological observation unit, at the same time as Lucia de Berk, that she had said during outdoor-exercise: “I released these 13 people from their suffering”. However, during the appeal, the man withdrew his statement, saying that he had made it up. The news service of the Dutch Broadcasting Foundation (NOS), and other media that followed the process, considered the withdrawal of this evidence as a huge setback for Public Prosecution Service (OM). A series of articles appeared over the following years in several newspapers, including Vrij Nederland and the Volkskrant, raising doubts about the conviction.

The case was next brought to the Supreme Court, which ruled on March 14, 2006 that it was incorrect to combine life imprisonment with subsequent psychiatric detention. Other complaints were not taken into consideration, and the evidence from the Strasburg analysis was not considered relevant. The Supreme Court gave the matter back to the Court in Amsterdam to pass judgement again, on the basis of the same factual conclusions as had been made before. Some days after the ruling of the Supreme Court, de Berk suffered a stroke and was admitted to the hospital of Scheveningen prison. On July 13, 2006, de Berk was sentenced by the Court of Appeal in Amsterdam to life imprisonment, with no subsequent detention in psychiatric care.


A committee of support for Lucia de Berk was formed that continued to express doubts about her conviction. Philosopher of science Ton Derksen[1], aided by his sister, geriatrician Metta de Noo-Derksen, wrote the (Dutch language) book Lucia de B: Reconstruction of a Miscarriage of Justice.[2] They doubted the argumentation used by the court and the medical and statistical
evidence that was presented. See also Derksen and Meijsing (2009)[3].

Chain-link proof

Of the seven murders and three attempted murders finally attributed to de Berk by the court, two were considered by the court proven by medical evidence. According to the court, de Berk had poisoned these two patients. The court then applied a so-called chaining-evidence argument. This means that if the several (attempted) murders have already been established beyond reasonable doubt, then much weaker evidence than normal is quite sufficient to establish that a subsequent eight “suspicious incidents” are murders or attempted murders carried out by de Berk.

For the two murders found proven by the court in The Hague, many experts do not exclude a natural cause of death. In the case where digoxin poisoning was alleged, and supposedly detected by independent measurements in two Dutch laboratories, the (same) method used in those laboratories did not exclude that the substance found was actually a related substance naturally produced in the human body. The Strasburg laboratory used a new method, a test of high specificity and sensitivity, and did not support the digoxin overdose hypothesis. In the second case, the intoxication could well have been an overdose caused by a faulty prescription. For both children, the question moreover remained, how and when De Berk was able to administer the poison. Regarding the digoxin case, the prosecution gave a detailed reconstruction of the timing. However, other parts of the evidence, discarded by the prosecution, showed by the timestamp on a certain monitor that at the alleged moment of poisoning Lucia was not with the patient at all, and that the specialist and his assistant were with the patient at that time.

The prosecution initially charged de Berk of causing thirteen deaths or medical emergencies. In court, the defense was able to show definitively that de Berk could not have been involved at all in several of these cases. For instance, she had been away for several days; the idea that she was there was due to administrative errors. Furthermore, it should be pointed out that all deaths had been registered as natural, with the exception of the last event. Even that last event was initially thought to be a death by natural cause by the doctors responsible for the child, but within a day, on being connected with de Berk and her repeated presence at recent incidents by other hospital authorities, it became an unnatural death.

Statistical proof

Lucia de Berk was not caught “red-handed”, and has always denied guilt, so the prosecution relied on other, indirect evidence. Among other things, the court made heavy use of statistical calculations to achieve its conviction. In a TV special of NOVA,[4] Dutch professor of Criminal Law Theo de Roos stated: “In the Lucia de B. case statistical evidence has been of enormous importance. I do not see how one could have come to a conviction without it”. The law psychologist Henk Elffers, who was used by the courts as expert witness on statistics (both in the original case and on appeal), is also interviewed here, and states that the chance of a nurse working at the three hospitals being present at the scene of so many unexplained deaths and resuscitations is one in 342 million. The probability of one in 342 million, calculated by the law psychologist Elffers, is extremely controversial.[5] The hospital and the prosecution decided in advance that the deaths had been caused by a nurse, and Lucia de Berk soon became the only suspect, because there were ‘rumours’ going on about her.[6]

The use of multiplication of probabilities for the three wards by the law psychologist Elffers was incorrect: if one wishes to combine p-values (right tail probabilities) of the statistical tests based on data from three separate wards, one must introduce a correction according to the number of tests, as a result of which the chance becomes one in a million (Fisher’s method for combination of independent p-values).[7][8] In the summing up after the appeal, the Court claims no longer to have used statistical arguments. This claim, which is in complete contradiction with the statement of the professor of Criminal Law Theo de Roos, cited above, that a conviction would not be possible without it, was also issued to the Dutch newspapers.

If one reads the verdict, one notices that statistical reasoning is still present everywhere. It was considered clear that so many incidents could not have occurred by chance. Derksen has reported to the committee, chaired by the lawyer Grimbergen (which was a part of CEAS, consisting of committees for reevaluation of closed cases, chaired by Y. Buruma), that the number of incidents that occurred during de Berk’s shifts were too large, and the numbers for other nurses were too small. Correcting those figures, increases the chance to about one in fifty. The statisticians Richard Gill and Piet Groeneboom arrive at a chance of one out of twenty-five that a nurse can experience a sequence of bad luck of the same type as Lucia de Berk.[9] In the judges’ summation, evidence is selected from many different medical experts, in order to argue that each of the incidents to be attributed to de Berk was indeed an unnatural death or near-death. Sometimes specialist A is preferred above specialist B, sometimes the other way around, sometimes another, C. In that case, C is arguably the most expert person, because he alone considered the incident unnatural. In another case there is only one expert who considers the death unnatural. He actually stated that he only has this opinion because de Berk was present and she had been present at so many other incidents. This is not mentioned in the judge’s conclusion.

Professor Piet Groeneboom[10] has drawn attention to the lack of professionalism of the people who made very strong statements of statistical nature at the start of the case (such as the chance of one in 342 million of the law psychologist Elffers) and the fact that neither the courts nor the Grimbergen committee consulted a real statistician or professor of mathematical statistics. Only after the committee had been studying the case for a whole year and had been repeatedly addressed by statistician Professor Richard Gill, did it allow him to have a conversation with them.

Professor Philip Dawid (professor of statistics, Cambridge, UK) stated that law psychologist Elffers “…made very big mistakes. He was not sufficiently professional to ask where the data came from and how accurate the data were. Even granted the data were accurate, he did some statistical calculations of a very simplistic nature, based on very simple and unrealistic assumptions. Even granted these assumptions, he had no idea how to interpret the numbers he got”.[11] Professor DasGupta, a toxicologist from the University of Houston, (Texas, USA) commented on the complete lack of toxicological evidence with
regard to the claimed digoxin intoxication.[11]

The use of probability arguments in the de Berk case was discussed in a 2007 Nature article by Mark Buchanan. He sums up the views of Ton Derksen as follows:

The court needs to weigh up two different explanations: murder or coincidence. The argument that the deaths were unlikely to have occurred by chance (whether 1 in 48 or 1 in 342 million) is not that meaningful on its own – for instance, the probability that ten murders would occur in the same hospital might be even more unlikely. What matters is the relative likelihood of the two explanations. However, the court was given an estimate for only the first scenario.[12]

At the initiative of Richard Gill, a petiton for a reopening of the Lucia de Berk case has been started. On November 2, 2007 the signatures, which were on the list at that time, have been presented to the Minister of Justice Ernst Hirsch Ballin and the State Secretary of Justice Nebahat Albayrak. Over 1300 people signed the petition by now. Among the people who signed the petition are many scientists from all over the world. In the Netherlands almost all professors of statistics and probability signed the petition [13].

The Diary

Lucia de Berk’s diary also played a role in her conviction. On the day of death of one of her patients (an elderly lady in a terminal stage of cancer) she wrote that she had ‘given in to her compulsion.’ She wrote on other occasions that she had a ‘very great secret,’ and wrote that she was concerned about ‘her tendency to give in to her compulsion.’ De Berk stated that this referred to her passion for reading tarot cards, whereas the court decided it was evidence that she had euthanized the patients. De Berk explains that she did this in secret, because she did not believe it appropriate to the clinical setting of a hospital. According to the court, the reading of cards does not accord with a compulsion nor with perhaps an expression of fatigue as she described it at the time. The daughter of de Berk, Fabiënne, explained in an interview on the television program Pauw & Witteman that some of her mother’s notes in the diaries are ‘pure fiction,’ which she wanted to use for a thriller.

The Dutch Forensic Institute (NFI) report

After the appeal proceedings were closed, but before the judges delivered their verdict, the Public Prosecution Service received, via the NFI, a report from a prestigious forensic laboratory in Strasbourg. This had been requested by the NFI who had hoped that it would support the hypothesis of digoxin poisoning. In fact, the NFI wrote to Strasburg that they were hoping for a miracle. The report subsequently lay in a drawer of the NFI for two years, but it did turn up in time for the final evaluation of the case before the Supreme Court. According to the Public Prosecution, the report contained no new facts, but according to de Berk’s defence the report proved that there was not a lethal concentration of digoxin in the first case. The Supreme Court accepts the facts reported by the judges at the appeal court, and is concerned only with jurisprudence and correctness of the sentence, given those facts. The report therefore was not admitted to the final considerations of the sentence given to de Berk.

Posthumus II Commission

In general, in the Dutch law system, cases are not re-opened unless a new fact, called “novum”, is found. New interpretations by experts of old facts and data are generally not considered a novum.[14]

In spite of this, Ton Derksen submitted his and Metta de Noo’s research on the case, to the Posthumus II Commission. This ad hoc, non permanent commission examines some selected closed cases and looks for evidence of errors in the police investigation regarding “tunnel vision” and misunderstanding of scientific evidence. Derksen pointed out that the medical experts who had ruled out the possibility of death by natural causes had not been given all relevant information, that the hypothesis of digoxin poisoning was disproven, in particular by the Strasburg analysis, and that the statistical data was biased and its analysis incorrect, and the conclusions drawn from it invalid. The commission announced on 19 October 2006 that this is one of the few cases it will consider in detail. Three wise men, recruited by the Public Prosecution service from the full Posthumus II committee, considered the following matters, having been instructed to focus on possible blemishes in the criminal investigation:

  • Whether there were also unexplained deaths when Lucia de Berk was not present, unknown to the public prosecutor.
  • Whether the expert witnesses were given all relevant available information.
  • Whether scientific knowledge now throws a different light on digoxin question.

In October 2007, the commission released its report[15][16][17] and recommended that the case be re-opened. They concluded that the case had been seriously marred from the start by tunnel-vision. In particular, the same persons, chosen from close circles of the hospital authorities rather than on the basis of recognised, relevant, expertise, had first helped the hospital in its internal investigations, then had advised the police, and finally had appeared before the courts as independent scientific experts. They noted that there was strong disagreement concerning whether or not baby Amber had died of digoxine poisoning. On the April 2, 2008, de Berk was released for three months because indeed, after re-examining the death of her last victim, a natural death could no longer be ruled out.

Case reopened

On June 17, 2008, Advocate-General of the Supreme Court, mr. G. Knigge, made a request for the Dutch Supreme Court to reopen the case, which was done on October 7, 2008.[18] The court acceded to his request on October 7, 2008, acknowledging that new facts uncovered by Knigge substantially undermine earlier evidence.[19] In particular, an independent team of medical researchers with access to all available medical information had reported to Advocate-General Knigge that the death which sparked the case appears to have been a natural death. The key toxicologist of the earlier trials had agreed with the new medical findings, pointing out that at the time of the trial, the court had only given him partial information about the medical state of the child. Lucia’s statements about her doings on the night of that child’s death had also been shown to be correct; indeed, during the period in which the courts had earlier concluded that she must have administered poison, the baby was actually being treated by a medical specialist and his assistant. H
er claim of innocence of that child’s death can no longer be taken to be a lie. Since there is no proof that she lied concerning the events around the death of baby Amber, it is no longer possible to assume that other statements of hers concerning earlier events are necessarily untrue, whenever they happened to disagree with earlier conclusions of the court. Lucia de Berk is allowed to wait in freedom for a retrial at the Court of Arnhem which is presently (November, 2009) adjourned while further investigations are made. The public prosecution had asked for extensive new forensic investigations, but this request was turned down by the court. Instead it has commissioned further independent medical investigations into the cases of two more of the children, again allowing a multidisciplinary medical team access to all possible medical data concerning the children. At a sitting of the court in Arnhem on 9 December 2009, the court stated that new integral medical investigations of the last nine months have confirmed that the cases of Amber, Achmed, Achraf are all natural deaths/incidents. (These are the only ones where there was formerly even a semblance of proof). The court will need less than a day to wind things up, on March 17, 2010. In the meantime: no more investigations, no more experts.

See also

  • Serial killers in the Netherlands
  • Miscarriages of justice in the Netherlands
  • Sally Clark
  • Prosecutor’s fallacy


  1. ^ (Dutch)Dutch wikipedia article on Derksen
  2. ^ Ton Derksen (2006). Lucia de B. Reconstructie van een gerechtelijke dwaling. Veen Magazines BV. ISBN 90-8571-048-0. 
  3. ^ The Fabrication of Facts: The Lure of the Incredible Coincidence, Ton Derksen and Monica Meijsing. pp. 39-70 in: Legal Evidence and Proof, H. Kaptein, H. Prakken and B. Verheij (eds), Ashgate, isbn 978-0-7546-7620-1, 2009
  4. ^ Statistiek in het strafproces NOVA/Den Haag Vandaag, 4 November, 2003
  5. ^ Goldacre, Ben. “Losing the lottery/” The Guardian. April 7, 2007.
  6. ^ PDF “Bevindingen over het functioneren van de Commissie Evaluatie Afgesloten Strafzaken 2006-2008.”
  7. ^ R. Meester, M. Collins, R.D. Gill, M. van Lambalgen (2007). “On the (ab)use of statistics in the legal case against the nurse Lucia de B“. Law, Probability and Risk 5: 233. doi:10.1093/lpr/mgm003. 
  8. ^ Discussion of Collins et al. by David Lucy
  9. ^ Gill, R.D., and Groeneboom, P. “Elementary Statistics on Trial.” January 31, 2009
  10. ^ Groeneboom, Piet. “Lucia de Berk and the amateur statisticians.” May 28, 2007.
  11. ^ a b “Expert on the most important proof in the Lucia de B. case: “This baby has not been poisoned”.” NOVA. September 29, 2007.
  12. ^ Mark Buchanan (18 January 2007). “Statistics: conviction by numbers“. Nature 445 (7125): 254–255. doi:10.1038/445254a. 
  13. ^ Persbericht CWI Petitie 2 november 2007
  14. ^ – Binnenland – Gerechtshof wil niet horen van rechterlijke fouten
  15. ^ Hoge Raad verklaart de aanvrage tot herziening in de zaak Lucia de B gegrond” (in Dutch). 7 October 2008. Retrieved 12 November 2008. 
  16. ^ Rapport Commissie evaluatie afgesloten strafzaken inzake mevrouw de B. October 29, 2007 (in Dutch)
  17. ^ Report of the CEAS triumvirate in the case against Mrs. de B. October 29, 2007 (partial English translation)
  18. ^ Hoge Raad verklaart de aanvrage tot herziening in de zaak Lucia de B gegrond” (in Dutch). 7 October 2008. Retrieved 12 November 2008. 
  19. ^ NRC “New trial for nurse convicted of seven killings” October 7, 2008


External links

  1. Site on statistical aspects of case, by Richard Gill, Professor of Mathematical Statistics at Leiden University.
  2. English summary of site of Dutch committee for Lucia de B. by Metta de Noo and Ton Derksen ( site removed ? )
  3. Three reasoning instincts and the fabrication of facts: the case Lucia de B., by Ton Derksen

NAME Berk, Lucia de
DATE OF BIRTH September 22, 1961
PLACE OF BIRTH The Hague, Netherlands

© This material from Wikipedia is licensed under the GFDL.

Retrieved from