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David L. Chadwick, M.D.1 and Rob Parrish, J.D.2
In recent years, a disturbing defense has surfaced in criminal cases involving shaken baby syndrome. This defense alleges that the child (who usually has typical SBS pathology) was, in fact, injured by an injection of DTP (diphtheria, tetanus toxoids and pertussis) vaccine rather than by an abusive act by another person.
Although numerous articles have dismissed the theory that the vaccine can cause permanent brain damage in infants, physicians who have qualified as 'experts' about children's brain injuries and diseases have testified that SBS pathology can be produced by the DTP immunizing injection. Prosecutors of shaken baby cases should be aware of this untrue defense and be prepared to exclude this irresponsible medical testimony.
Shaken baby syndrome describes a constellation of injuries which includes a disturbance of consciousness accompanied by recent subdural bleeding.3 Brain swelling and retinal hemorrhages are present in many cases and about half of the cases have findings of extracranial injury.4 Death or permanent brain damage are frequent outcomes in SBS.
The mechanism of injury in SBS is generally believed to be accelerating or decelerating movement of the head involving great force and occurring in shaking or slamming of the child.5 Some cases have evidence of impact injuries and may be termed shaken impact syndrome,6 but are otherwise identical to shaken baby syndrome cases.
The definition of SBS requires the exclusion of accidental injury and disease as causes of the pathology. The pathology may be found at autopsy, and in fatal cases, it includes the presence of recent subdural bleeding and brain swelling often of severe degree. The same findings can be determined in surviving children by the use of imaging techniques and other tests done during the early stages after initial presentation.
The pathology described for SBS is due to mechanical injury, and there are very few possible exceptions. Somewhat similar pathology has been ascribed to spontaneous bleeding in the subdural space that may occur with certain congenital malformations or with blood coagulation problems. However, no medical papers exist which propose that this pathology could be related in any way to DTP immunization.
Can Immunizations Cause Brain Damage?
The possibility that reactions to various vaccines might produce brain damage has been a subject of medical concern for decades. Because such events are either rare or non-existent, scientific analysis of risk has been difficult and expensive; however, at times these concerns appeared to be causing avoidance of immunizations and high expenses for vaccine manufacturers.7
These considerations led to the passage of the National Childhood Vaccine Injury Act in 1986.8 That legislation established a no-fault insurance program to compensate children who appear to have been injured by vaccines, but without requiring them to sue and establish a causal connection.
An auto-immune mechanism for vaccine injury has been proposed because it is demonstrable in some cases of rabies immunization in which an antigen containing brain tissue is used.9 However, the DTP vaccine contains no such materials and the demyelinating pathology caused by rabies vaccine has not been linked to other types of immunization. This is one of the problems that make study of this subject difficult. No specific pathology for DTP-associated brain injury has ever been found or even proposed.10
Very recent studies have not provided evidence to support a causal relationship between DTP immunization and serious acute neurologic illness resulting in permanent neurologic injury.11 A recent article from Great Britain flatly dismisses the theory that pertussis vaccine can cause permanent brain damage in infants, and notes that the "scare following publication of the mistaken theory that pertussis vaccine was a significant cause of brain damage is an example of what can happen when preliminary research is made public."12
Another study found that even among children who reportedly experienced a previous adverse reaction to a vaccination, revaccination resulted in another adverse event in only 17 percent of the children, and none were serious enough to require hospitalization.13
Recent work also summarizes the U.S. experience over the last few years since the shift to the general use of an acellular pertussis vaccine. That shift was based on a likelihood that the new vaccine (DpaT) would produce fewer reactions than the old one, and this has proved to be the case. No new information about a relationship of pertussis vaccine reactions to the pathology seen in SBS was acquired in this study.14
The DTP Defense in SBS Cases: A False Causal Connection
The idea that DTP injection might produce the pathology seen in SBS has begun to appear in testimony during the last few years in spite of the fact that it has not appeared in a peer-reviewed medical article. "Expert witnesses" seeking to link SBS cases to DTP immunization must create a false causal connection. This involves sophistry and a willingness to ignore all requirements for the determination of causality. They can sometimes make this connection in a courtroom where the triers of fact are medically naïve.
The DTP defense was raised unsuccessfully in the criminal prosecution of Dr. Malcolm Scoon, a New York anesthesiologist who was convicted of manslaughter for causing the death of his five-month-old daughter. Mariah Scoon exhibited all the classic signs and symptoms of shaken baby syndrome. Soon claimed that his daughter died as a result of infection, which in turn was caused by a vaccination received one week prior to her death. The jury rejected this claim and the case is pending on appeal.
In another case,15 the defense also claimed that shaken baby injuries were caused exclusively by an abreaction to a vaccination the twelve-week-old victim had received earlier on the day of his hospitalization. The expert witness called by the defense offered an opinion that the DTP shot may have contributed to death, and claimed that less than violent shaking might have caused his death. The county coroner testified that if the baby had died as a result of the pertussis toxin, he would have seen petechial hemorrhages throughout the brain, not acute subarachnoid and subdural hemorrhage as was present in this victim. The Court of Appeals found the defense expert's speculation was not credible and upheld the defendant's conviction of manslaughter.
In one of the few reported cases where the defense was successful in a jury trial, William Carey of Whitehouse, New Jersey, was acquitted of endangering his 5-month-old son's welfare in a 1998 trial. The defense theory was that the victim had a preexisting bleeding disorder which was aggravated by the immunization, but even the defense attorney conceded that his expert witnesses did not explain the existence of bilateral, diffuse retinal hemorrhages, and he was surprised the prosecutor did not spend more time on that issue in closing argument.16
The Role of Irresponsible Expert Testimony
Irresponsible medical expert testimony has been defined by a number of authors and recently reviewed.17 A number of its forms have been described, of which an important one is 'unique causal theory.' Here, the 'expert' connects a cause and an effect in a way which has never been described in peer-reviewed medical literature. In short, the 'expert' invents the causal relationship for use in court in spite of the fact that it has no other existence.
Other forms of irresponsible expert testimony that may arise in a case with this defense include providing testimony outside of the witness's demonstrable area of expertise, inventing nonexistent medical findings in the case being litigated, omitting pertinent facts and outright false statements.
Medical expert testimony to the effect that DTP immunization might produce pathology of the type seen in SBS is clearly irresponsible. Although there is sometimes a temporal connection between reaction of a toddler or infant to a vaccination and inflicted head injuries, this is not particularly surprising given the additional stress of caring for a child who feels mild symptoms resulting from the vaccination. This temporal connection between head injuries and vaccination should not be mistaken for proof of a direct causal connection - such reasoning is not scientific, logical, or reliable enough for courtroom proof. In the absence of empirical evidence supporting the view that abreaction to DTP or other vaccines can directly cause the constellation of brain damage, intracranial bleeding and ocular damage, witnesses who purport to be able to draw such a conclusion should be prohibited from testifying in court.
Confronting the 'DTP Defense'
In spite of the fact that no medical papers propose that the pathology described for SBS could be related in any way to DTP immunizations, the 'DTP Defense' should concern prosecutors. In highly contested child abuse criminal trials, even speculative possibilities can be sufficient to raise a reasonable doubt concerning a perpetrator's guilt, since juries do not want to believe that caretakers are capable of violent assault on helpless children.
Judges in most jurisdictions have the tools available to limit or exclude such irresponsible testimony, which is scientifically unreliable and thus inadmissible. A motion in limine should be filed to keep an expert witness from offering irresponsible and unreliable testimony in a trial. If the testimony cannot be excluded, prosecutors and attorneys in child protection cases should be prepared to confront such irresponsible medical testimony with clear and detailed refutation from well-qualified experts. Preventing this type of untrue defense from being used is key to achieving verdicts based on evidence as opposed to unsupportable speculation.