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by: Brett Wilson
October 20, 2026
The practice of identifying individuals from bite marks has received considerable criticism in recent years and consequently the Court of Appeal were invited to consider the admissibility of evidence in relation to “bite-marks” in the case of R v Hedges [2025] EWCA Crim 1051.
Sian Hedges (H) was convicted of the murder of her 18 months old son Alfie along with her partner Jack Benham (B) at Maidstone Crown Court on 13 November 2023.
The events surrounding Alfie’s death occurred overnight between 27/28 November 2022, when only (H) and (B) were present in a caravan with Alfie. Alfie had been seen by others on the evening of 27 November without visible injuries, however on the morning of 28 November, he was found dead and showing signs of rigor mortis and hypostasis.
Subsequent postmortem examinations of Alfie recorded multiple bruising, abrasions and fractures, some said to have been caused within 12 hours of death and others within 72 hours of death. The examining pathologist concluded that Alfie’s cause of death was because of a significant and sustained assault, though he was unable to confirm whether the death was through asphyxiation or respiratory dysfunction.
Accordingly, the cause of death was recorded as “unascertained – unnatural causes”. In relation to some of the marks on Alfie’s body, the pathologist deduced that they may have been caused by biting.
Photographs of the marks were sent to a forensic odontologist Dr Philip Marsden, who concluded that injuries to Alfie’s forearm and back were “probable” bite marks and a third to the forearm was a “possible”. His categorisations were made using the British Association of Forensic Odontologists’ scale, namely exclusion, possible, probable, definite. Dr Marsden sought dental impressions of H and B and then compared the marks to the dental impressions. On comparison, he was unable to link the forearm bites to either of H or B, however, as regards the mark on Alfie’s back he was able to exclude B as his teeth did not match the unusual, rotated canine seen in the mark, but he could not exclude H.
It is important to note as the appeal court subsequently did, that Dr Marsden did not claim to positively identify Hedges as the biter, acknowledging others could have similar dentition as her.
The prosecution case was that both adults engaged in the assault, whereas the defendants claimed that the other was solely responsible for Alfie’s death. The significance of the bite mark evidence was that although it was not the direct cause of death, it was capable of undermining H’s defence that B was the sole cause. There was in addition text messages between H and B whereby admissions appeared to have been made to biting Alfie without causing injury.
H challenged the admissibility of the evidence of Dr Marsden and instructed Professor Iain Pretty a retired former forensic dentist.
Professor Pretty did not examine the evidence but contended that bite mark identification and comparison lacked a sufficiently strong scientific basis to be admissible evidence. He cited numerous studies demonstrating inconsistencies amongst odontologists when identifying bite marks. Additionally, Professor Pretty criticised Dr Marsden’s methodology and the reliance on photographs suggesting that the analysis by its nature was subjective.
The trial judge admitted the evidence of Dr Marsden, and in doing so noted the controversy of bite mark evidence, however he identified the tests of relevance and competency, asserting that the evidence was relevant and Dr Marsden competent, and further he indicated that Dr Marsden’s evidence was in line with good practice, and that there was no basis to exclude the evidence under Section 78 of the Police and Criminal evidence Act 1984.
H appealed, her counsel submitting that the field of Forensic Odontology was insufficiently regulated, that there was an absence of CPS guidance, as well as the fact that the British Association of Forensic Odontologists’ guidance lacked external evaluation and peer review. Professor Pretty’s research evidence that he had cited further served to cast doubt upon the scientific robustness of this evidence, and as a consequence it should not have been admitted.
In response, the Prosecution contended that Dr Marsden was highly experienced, that Professor Pretty had not examined the evidence, and importantly Dr Marsden did not make a positive identification but simply excluded B and did not exclude H. Further, the studies referred to by Professor Pretty were critical of the uniqueness of dentation, as opposed to bite mark comparison evidence.
In reviewing the admissibility of the evidence of Dr Marsden the Court of Appeal referred to the test for admissibility of expert opinion in Rule 7.1.1 of the Criminal Practice Directions, i.e. is the opinion relevant to a matter in issue, is it needed to provide the court with information likely to be outside the court’s own knowledge and experience, is the witness competent to give that opinion, and is the expert opinion sufficiently reliable to be admitted. If so, opposing views are for the jury to assess.
Accordingly, the Court of Appeal concluded that the evidence was relevant and necessary as the central issue was who caused Alfie’s injuries, and lay jurors could not assess bite marks unaided.
Their Lordships went on to distinguish the opinion of Dr Marsden and the discredited practice of identification of an individual based on bite marks, highlighting the cautious approach he had taken by not claiming uniqueness nor making a positive identification, but only serving to exclude the responsibility of the mark from being that of B. Additionally, their Lordships described his evidence as careful, cautious and in line with modern practice, and that Dr Marsden was competent having considerable experience and qualifications.
Their Lordships also cited the strength of the prosecution evidence in the case even without the admission of the bite mark evidence in that she had been present throughout the period when the injuries were caused highlighting the text evidence where she had admitted to biting Alfie on previous occasions, thereby indicating that the jury verdict was safe, as they were unlikely to have convicted H on the evidence of Dr Marsden alone.
In concluding that Dr Marsden’s evidence was unimpeachable, their Lordships confirmed that the science of forensic odontology has its limitations, however it was sufficiently robust for an expert to provide an opinion that as to whether a skin lesion was a bite mark or not. Moreover, the current state of the science does not allow experts to make a positive identification that a particular suspect caused the bite, although experts may exclude suspects from a pool of potential biters, with the ultimate weight and significance of the evidence being a matter for the jury to decide in the context of all other evidence in the case.
The Court of Appeal carefully navigated through the criticism of identification of individuals through bitemarks, holding that the case was not one of identification but exclusion, thus making this case the template for admission of such evidence and providing useful rationale for admissibility of expert evidence in general.
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