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Non Accidental Head Injury Cases (NAHI, formerly referred to as Shaken Baby Syndrome [SBS]) - Prosecution Approach

Updated: 5 November 2021|Legal Guidance, Domestic abuse , Violent crime


This guidance is intended to provide information on the stance taken by the Courts in relation to Non Accidental Head Injury ("NAHI") cases and to assist prosecutors in the approach and presentation of such cases.

The use of the term Shaken Baby Syndrome should now be avoided as it can be considered to have emotive connotations and, more importantly, does not adequately describe the range of causes of head injuries.

The preparation and marshalling of expert evidence is of the utmost importance in achieving just resolution of these cases. Only advocates who are experienced and expert in the field of what is contended to be the unexplained death of an infant should be instructed to prosecute such a case.

Part of the duty of the advocate will be to assist the court and the judge will invariably discuss the issues of medical evidence with the advocates so that the judge will be in a position to structure carefully the summing up to those issues and to identify which evidence goes to the resolution of those issues.

The Causes of NAHI: The Triad of Injuries

The brain is encased in three membranes. The one immediately surrounding the brain is the pia mater. The next one is the arachnoid. Between the pia and the arachnoid is the subarachnoid space. The third membrane, surrounding the brain and continuing down the body surrounding and protecting the spinal cord is the dura. Between the dura and the arachnoid is the subdural space, as well as veins running between the two membranes called bridging veins.

Generally, cases where NAHI is alleged depend on a trilogy of findings of intracranial injuries (the triad) consisting of:

  • Encephalopathy (defined as any disease of the brain affecting the brain's function)
  • Subdural haemorrhages (bleeding in the subdural space); and
  • Retinal haemorrhages (bleeding within the retina).

Whilst not entirely understood, the mechanism for these injuries is thought to be the shaking of the infant, with or without impact on a solid surface. This moves the brain within the skull, damaging the brain and shearing the bridging veins between the dura and the arachnoid and sometimes causing retinal haemorrhages. Nevertheless, despite medical uncertainty surrounding the mechanism, the triad of injuries is a strong medical pointer to the infliction of NAHI.

There have been challenges to the triad. Between 2000 and 2004 a team of professionals led by Dr Jennien Geddes conducted research concluding in "Geddes III" which challenged the supposed infallibility of the triad suggesting that there was one unified cause of the three intracranial injuries constituting the triad, not necessarily trauma. This became known as the unified hypothesis.

However, in R v Harris: R v Rock [2006]1 Cr App R 5, Dr Geddes accepted that the hypothesis in this paper was not a credible challenge to the triad and was intended only to promote discussion. Attempts to rely on the unified hypothesis as a challenge to the triad are now rarely encountered and should always be subject to thorough testing. For further discussion, please see: R v Henderson; R v Butler: R v Oyediran [2010]2 Cr App R 24 at para. 69.

Those challenging the triad on occasions have also invited consideration of bio-mechanical evidence. There is, however, little data relating to the distance an infant would have to fall to suffer such injury to the head. Most experts also accept the difficulty for any biomechanical model to simulate the complex anatomy of an infant's brain.

Please see Annex A for a fuller discussion of the issues concerning biomechanics in NAHI.

Expert Evidence - The Legal Framework

Cases which depend on the triad inevitably involve consideration of complex expert evidence.

Whilst some of the cases below do not involve NAHI, their principles apply equally to such cases.

In R v Cannings (Angela) [2004] 1 W.L.R. 2607, the Court of Appeal quashed the appellant's convictions for murder where the only evidence against her was provided by experts. The issue was whether the two unexplained deaths of her infant sons were natural SIDS (Sudden Infant Death Syndrome) or had an unnatural but unknown cause. Following her convictions, the Court of Appeal received fresh evidence of a substantial body of research suggesting that such deaths could and did occur naturally even when they were unexplained. In quashing the convictions, the Court, at para.178, stated:

In cases like the present, if the outcome of the trial depends exclusively or almost exclusively on a serious disagreement between distinguished and reputable experts, it will often be unwise, and therefore unsafe, to proceed.

For a time, this judgment was taken to mean that where there was a conflict between expert witnesses, the prosecution case was effectively neutralised in the absence of evidence independent of such testimony. This contention was rejected by the Court of Appeal in the more recent case ofR v Kai-Whitewind [2005] EWCA Crim 1092, describing it as the "overblown 'Cannings' argument". Such an approach should only be applied, in the light of contemporary medical knowledge, to cases which depended solely on the inferences based on coincidence or the unlikelihood of two or more infant deaths in the same family.

In other cases, where there is a disagreement between experts about the interpretation of findings, such a dispute does not extinguish the findings themselves. In such cases, it remains for a jury to evaluate the expert evidence.


Cases which involve the triad must be approached with caution. In R v Henderson: R v Butler: R v Odeyiran [2010] 2 Cr App R 24 it was stated:

Where the prosecution is able, by advancing an array of experts, to identify a non-accidental injury and the defence can identify no alternative cause, it is tempting to conclude that the prosecution has proved its case. Such a temptation must be resisted. In this, as in so many fields of medicine, the evidence may be insufficient to exclude, beyond reasonable doubt, an unknown cause. (para. 1)

We emphasise that we are dealing with natural causes of death within the purview of up-to-date medical knowledge because in this appeal we were properly reminded that at no stage can knowledge in a field such as this be regarded as complete and comprehensive. There are limits to the extent of knowledge and no conclusion should be reached without acknowledging the possibility of an unknown cause emerging into the light of medical perception and that the mere exclusion of every possible known cause does not prove the deliberate infliction of violence. (para. 21)

The Court emphasised:

Where relevant, the jury should be reminded that medical science develops and that which was previously thought unknown may subsequently be recognised and acknowledged. In such a case the jury should be reminded that special caution is needed where expert opinion evidence is fundamental to the prosecution

In a case where a child dies (or suffers serious injury), as the above makes clear, it is rare that a charge of homicide (or attempted murder or assault) could be sustained where the only evidence available is the triad of pathological features. Such evidence is rarely conclusive of NAHI and prosecutors should look for other, supporting evidence.

Sometimes, the evidence is in the form of additional medical evidence. In Henderson, in addition to the triad, the prosecution relied upon the evidence of retinal folds and axonal damage (damages to the nerve fibres). In Oyediran the prosecution relied upon evidence of a small bruise on the inner surface of the scalp and a previous arm fracture.

The 2016 report entitled Sudden Unexpected Death in Infancy and Childhood: the Report of a Working Group convened by The Royal College of Pathologists and The Royal College of Paediatrics and Child health identified a list of non-exhaustive factors that could suggest a death was suspicious and could provide supporting evidence of NAHI:

  • Previous on-going child safeguarding concerns;
  • Previous sibling deaths;
  • Delay in seeking help;
  • Inconsistent explanations;
  • Unexplained injury, either present or previously;
  • Evidence of past or present drug and/or alcohol abuse;
  • Neglect;
  • Previous convictions of parents or partners, in particular violence towards children.

All of the surrounding evidence must be fully considered by a prosecutor before a decision can be made on the evidential sufficiency of any case in accordance with the Full Code test in the Code for Crown Prosecutors.

The level of charging will have to be considered carefully in the light of the comments in R v Allen (Tony) [2005] EWCA Crim 1344 and Harris and Others as to whether the necessary intent can be inferred from the degree of force believed to have been used. Regard must be had to the expert evidence as to the level of force and duration of assault.

In appropriate cases where death has occurred, prosecutors may wish to consider a charge contrary to Section 5 of the Domestic Violence, Crime and Victims Act 2004 as well as murder or manslaughter. Guidance on the implications of this course can be found in the CPS Legal Guidance on Homicide.

The Role of the Expert

If an infant has died, a post-mortem will have been conducted by a paediatric pathologist. Where a criminal investigation is on-going or where significant concerns have been raised about the possibility of abuse or neglect contributing to the infant's death, a forensic pathologist should accompany the paediatric pathologist and the joint post-mortem examination protocol should be followed.

Consideration will need to be given to instructing a range of experts who should not be the attending clinicians who treated the infant at the time of the admission to hospital.

Such experts will include consultants with expertise in the fields of:

  • Paediatric neurosurgery;
  • Paediatric neuroradiology;
  • Paediatric radiology;
  • Paediatric histopathology;
  • Paediatric ophthalmology; and
  • Paediatric neuropathology.

It is sometimes of assistance to instruct an immunologist if issues about infection are raised.

Ultimately, a consultant paediatric intensivist can provide an overall framework in which the large amount of different specialisms can be understood.

Guidance on the prosecution disclosure obligations in respect of expert witnesses is provided in Chapter 36 of the Disclosure Manual and should always be referred to when any expert is instructed.

The Court of Appeal in Henderson placed significant emphasis on the issue of whether or not an expert was in clinical practice at the time of the report in determining the admissibility of any expert's report further to the Criminal Procedure Rules.

Guidance as to the correct approach to the management of such cases was given by the Court in Henderson, where it was stated that a conviction based merely on the evidence of experts could only be regarded as safe if the case proceeded on a logically justifiable basis for rejecting or accepting the evidence.

The Criminal Procedure Rules: Part 19

Proper and robust pre-trial management is essential and the rules provided in Part 19 of the Criminal Procedure Rules ("CrimPR") should be adhered to strictly.

Rule 19.2(1) provides that an expert must help the court to achieve the overriding objective by giving opinion which is:

  1. Objective and unbiased, and
  2. Within the expert's area of expertise.

By Rule 19.6(4), a party may not introduce expert evidence without the court's permission if the expert has not complied with a direction under this rule.

In particular, this part of the Rules provides that it is the obligation of the expert to define their area or areas of expertise (19.2(3)(a) CrimPR) and, when giving evidence in person, to draw the court's attention to any question to which the answer would be outside the expert's area or areas of expertise.

Rule 19.6(2) is also of importance. As part of the court's case management powers, a judge may direct the experts to:

  1. Discuss the expert issues in the proceedings; and
  2. Prepare a statement for the court of the matters on which they agree and disagree, giving their reasons.

In Henderson, the Court of Appeal stated that it would generally expect a meeting to be held so that a statement could be prepared well in advance of the trial. Such a meeting should be attended by all significant experts, including the defence experts. A careful, detailed set of minutes would need to be taken and signed by all the participants. It would be preferable that the legal representatives did not attend.

It is difficult to envisage a case involving an allegation of NAHI where such a meeting would not take place.

InR v Reed and Reed: R v Garmson [2010] 1 Cr App R 23, the court dealt with the complex science of admissible DNA evidence. There is useful guidance in that case which is applicable to complex NAHI medical evidence, in particular a 'primer' or guide to the basic science applicable to be agreed and provided to the jury.

A judge could also exercise their powers of case management under the CrimPR to ensure that, in advance of a trial, a defence expert made disclosure of any relevant previous reports and any adverse judicial criticism. A case management hearing could present an opportunity for concerns as to previous criticism of an expert and an expert's previous tendency to travel beyond their area of expertise. Such a history would not necessarily be a ground for refusing the admission of the evidence but it could raise issues about the advisability of relying on such a witness.

Parallel Proceedings: Family and Criminal

Where there are associated family proceedings, as well as a criminal investigation, regard should be had to the Legal Guidance on Children as Victims and Witnesses , in particular the section on Family Proceedings. Prosecutors should consider making enquiries through the police of the local authority solicitors about the family proceedings.

In addition to seeking disclosure from the Family Court proceedings, the legal guidance provides guidance on disclosure of criminal material to the Family Courts.

Regard should also be had to the Legal Guidance - Disclosure of Material to Third Parties.

It is important that all information sharing takes into account the guidance in the Child Abuse Protocol: 2013 Protocol and Good Practice Model – Disclosure of Information in Cases of Alleged Child Abuse and Linked Criminal and Case Directions Hearings at

Annex A: Biomechanics in Non Accidental Head Injuries (NAHI)

The study of biomechanics is the practice of applying the principles of mechanics to biological systems.

Some specialists, medical and non-medical, in Child Abuse and NAHI cases believe that evidence of biomechanical studies should not be part of the complex investigation and prosecution of such cases.

One straightforward problem is that the dummies do not replicate the particular human structures that are central to the 'triad of injuries'; they have no brain, eyes or venous architecture (network of veins). It is also worth noting that the neck mechanism in such dummies only replicates movement in one direction (backwards and forwards) and does not reflect the range of movement possible in a baby or child.

These dummies are designed to replicate a forward and backward movement, with no capacity for side to side or angular movements. The skull of a child is flexible due to immaturity and, dependent upon age and birth circumstances, the sutures (areas of the skull) are not yet fused. By contrast, the fibreglass skull of the dummy is solid; it is made of several layers of fibreglass matting, coated with resin and allowed to react with a catalyst which causes the fibreglass to set vary hard.

A human brain is of course set within fluid, with a complex bridging vein structure; the Child Restraint Air Bag Interaction dummy (“CRABI") skull (see below) contains a metal box set within the fibreglass skull with data cables and sensors attached.

Depending on the age of a child, no response values are considered if, for example, a child is old enough to break their fall by placing hands or arms out before impact. The dummy arms and legs are bolted on and set to a certain G-force of response in an attempt to replicate immature knee joint responses.

Outlined below is a basic description of a widely used model in bio mechanical studies, the CRABI.

CRABI (Child Restraint Air Bag Interaction dummy)

The CRABI is used to evaluate air bag exposure to infants restrained in child safety seats that are placed in the front seat. CRABI dummies come in three sizes: 6-month-old, 12-month-old and 18-month-old.

Child Restraint Air Bag Interaction dummy

Figure 1 CRABI Dummy

The CRABI was only intended to be used in this context. It was never intended to be used in experiments to replicate paediatric internal head injury as seen at hospital and at post mortem.

The CRABI 12-Month Old was developed in 1993 by a Society of Automotive Engineers (SAE) Task Force for the purpose of testing forward and rearward facing child restraints.


The skull is manufactured from fibreglass with a steel weldment insert, and the head skin is moulded urethane. An upper neck load cell simulator is assembled with the head to allow for installation of three uniaxial accelerometers in a triaxial configuration at the centre of gravity (CG). A separate uniaxial accelerometer can be installed at the rear of the accelerometer mount to measure angular acceleration in the sagittal plane.

CRABI Dummy Head

Figure 2 CRABI Dummy Head


A flexible moulded rubber neck is used to give the head assembly human-like flexion and extension characteristics. A six-axis load cell can be mounted at both the upper and lower ends of the neck assembly.

CRABI Dummy Neck

Figure 3 CRABI Dummy Neck


Chest foam and a chest foam support assembly mounted on a thoracic spine box make up the upper torso. The shoulders are made of flexible rubber joints. A two-axis load cell can be mounted in each shoulder. The thoracic spine is a welded aluminium structure that provides a mounting location for the triaxial configuration accelerometers at the T1 vertebrae.

The pelvis/lumbar assembly includes a welded aluminium pelvic structure and a flexible moulded rubber lumbar spine. A six-axis load cell may be mounted between the base of the lumbar spine and the top of the pelvis. The pelvic aluminium structure also provides space for triaxal configuration accelerometers which are mounted at the bottom of the lumbar. The pelvis also can accommodate an optional two-axis pubic load cell. The abdominal insert is made of an open cell urethane foam. The torso flesh is moulded urethane with nylon netting reinforcement.

CRABI Dummy Torso

Figure 4 CRABI Dummy Torso (image 1)

CRABI Dummy Torso

Figure 5 CRABI Dummy Torso (Image 2)

Further reading

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