Thursday, April 15, 2010





"Lucia de Berk, often called Lucia de B. or Lucy de B (born September 22, 1961 in The Hague, Netherlands) is a Dutch licenced paediatric nurse, who was sentenced to life imprisonment in 2003 for four murders and three attempted murders of patients in her care," the Wikipedia account begins.

"After an appeal, she was convicted in 2004 of seven murders and three attempts. Her conviction is controversial in the media and amongst scientists, and has been questioned by investigative reporter Peter R. de Vries," the account continues.

"In October 2008, the case was reopened by the Dutch supreme court, as new facts had been uncovered that completely undermined the previous verdicts. De Berk was set free, and her case was re-tried; she was exonerated in April 2010.


As a result of an unexpected death of a baby (Amber) in the Juliana Children's Hospital (JKZ) in The Hague on 4 September, 2001, earlier deaths and resuscitations were scrutinised. 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 her.

Life sentence

On 24 March 2003, de Berk was sentenced by the court in The Hague to life imprisonment for the murder of four patients and the attempted murder of three others. The verdict depended in part on a statistical calculation, according to which the probability was allegedly 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 18 June 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 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 to be 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 Netherlands Supreme Court, which ruled on 14 March 2006 that it was incorrect to combine life imprisonment with subsequent psychiatric detention. Other complaints were not taken into consideration, and the evidence from a re-analysis by a Strasbourg laboratory 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, aided by his sister, geriatrician Metta de Noo-Derksen, wrote the (Dutch language) book Lucia de B: Reconstruction of a Miscarriage of Justice. They doubted the reasoning used by the court and the medical and statistical evidence that was presented. See also the English-language article Derksen and Meijsing (2009).

Chain-link proof

Of the seven murders and three attempted murders finally attributed to de Berk by the court, the court considered two 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 sufficient to establish that a subsequent eight “suspicious incidents” are murders or attempted murders carried out by the same defendant.

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 Strasbourg 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 of 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 de Berk 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 defence 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 causes by the doctors responsible for the child, but within a day, on being connected by other hospital authorities with de Berk and her repeated presence at recent incidents, 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 2003 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, was also interviewed on the programme and stated 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. 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' about her.

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). 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 was 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. 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 has drawn attention to the lack of professionalism of the people who made very strong statements of a 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.

Philip Dawid, Professor of Statistics at the University of 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”. 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.

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.

At the initiative of Richard Gill, a petition for a reopening of the Lucia de Berk case was started. On November 2, 2007 the signatures which were on the list at that time were presented to the Minister of Justice, Ernst Hirsch Ballin, and the State Secretary of Justice, Nebahat Albayrak. Over 1300 people have signed the petition, amongst them many scientists from all over the world and almost all professors of statistics and probability in the Netherlands.


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 that she was concerned about 'her tendency to give in to her compulsion'. De Berk has stated that these were references to her passion for reading tarot cards, which she explains she did secretly because she did not believe it appropriate to the clinical setting of a hospital. However, the court decided they were evidence that she had euthanised the patients. 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. De Berk's daughter Fabiƫnne 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 intended to use in writing a thriller.

Dutch Forensic Institute report

After the appeal proceedings were closed, but before the judges delivered their verdict, the Public Prosecution Service received, via the Netherlands Forensic Institute (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 Strasbourg 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 into the final considerations of the sentence given to de Berk.

Posthumus II Commission

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

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 selected closed cases and looks for evidence of errors in the police investigation indicating "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 Strasbourg analysis, and that the statistical data were biased and the analysis incorrect, and the conclusions drawn from it invalid. The commission announced on 19 October 2006 that this was one of the few cases it would 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 threw a different light on the digoxin question.

In October 2007, the commission released its report 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 digoxin poisoning. On 2 April 2008, de Berk was released for three months because after re-examination of the death of the last victim, a natural death could no longer be ruled out.

Case reopened

On 17 June 2008, the Advocate-General of the Supreme Court, G. Knigge, made a request for the Supreme Court to reopen the case. On 7 October 2008 the court acceded to his request, acknowledging that new facts uncovered by Knigge substantially undermined earlier evidence.[18][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. De Berk'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. Her claim of innocence of that child's death can no longer be taken to be a lie. Since there was no proof that she lied concerning the events around the death of baby Amber, it was no longer possible to assume that other statements of hers concerning earlier events are necessarily untrue when they disagreed with earlier conclusions of the court.

Lucia de Berk was allowed to wait in freedom for a retrial at the Court of Arnhem, which first adjourned while further investigations were made. The public prosecution had asked for extensive new forensic investigations, but this request was turned down by the court. Instead it 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 session on 9 December 2009, the court stated that new integral medical investigations of the last nine months had confirmed that the cases of Amber, Achmed and Achraf were all natural deaths/incidents. (These are the only ones where there was formerly any appearance of proof of de Berk's culpability.) No further investigations or expert testimony are required.

Last interogations of the new key witness Meulenbelt and the accused Lucia de Berk by the court took place on 17 March 2010. This confirmed that the deaths at the Juliana Children's hospital were natural, sometimes caused by wrong treatment or bad hospital management, and sometimes unexpected because of faulty medical diagnosis. The behaviour of the nurses, including de Berk, during a couple of medical crisis situations turned out to have been exceptionally professional: swift and effective, saving lives on several occasions. The Public Prosecution capitulated, formally requesting the court to deliver a "non-guilty" verdict.

On 14 April 2010, the court delivered the "non-guilty" verdict."

The account can be found at: