I, R & T, R. v

Expert scientific evidence based on a recognised and reliable test is not inadmissible merely because the test is used in a new context or for a new purpose. Apparent anomalies in the particular results, and untested possible explanations for them, ordinarily concern the weight of the evidence and whether the prosecution can prove its case, rather than admissibility. A trial judge must distinguish between the reliability of the scientific technique itself and the evidential sufficiency of its application to the facts.

The prosecution appealed under section 58 of the Criminal Justice Act 2003 from a ruling of His Honour Judge Sampson in the Crown Court at Kingston-upon-Hull.

The respondent company operated a plant processing animal by-products. It and its directors were charged with failing to heat blood to the prescribed temperature before its disposal as fertiliser. The prosecution relied on CIE testing, which detected animal proteins in samples taken from the plant and its distribution system.

The judge accepted that CIE was a recognised and reliable test for animal proteins. He nevertheless excluded the results because their coexistence with an absence of specified bacteria, and other perceived anomalies, created a reasonable doubt about reliability in this novel context. The issue was whether those matters made the expert evidence inadmissible or instead affected its weight and sufficiency.

1. Appeal allowed. The CIE results were admissible through the evidence of Mr Reaney, an acknowledged expert in the technique.

2. The trial judge had found that CIE was a well-recognised and reliable method for establishing whether animal protein was present in blood, and that heating above the relevant temperature denatured the proteins so that they would not be detected. Those findings supported admissibility. The fact that the test was used to establish whether proteins had survived processing at this plant, rather than for its previously established use of distinguishing species, did not itself make either the technique or its results unreliable.

3. The absence of specified bacteria in samples that tested positive for animal protein could potentially weaken the prosecution case. There were possible explanations, including dilution by processed blood or the addition of a bactericide. The prosecution had not adduced evidence sufficient to establish those explanations, and one explanation was accepted to be fanciful. However, the trial judge had not found the remaining explanations scientifically unsound, and the absence of proof for them did not establish that CIE itself was unreliable.

4. The judge therefore conflated admissibility with the separate question whether a jury could safely convict on the evidence. If the expert's explanations were improbable, the prosecution might fail to prove its case. That was a matter for assessment of the evidence at trial, not a basis for excluding an otherwise reliable scientific technique.

5. The Court ordered the proceedings on the indictment to be resumed in the Crown Court. The trial judge would determine any further application by the respondents on the evidence then available.

• Court of Appeal (Criminal Division): Allowed the prosecution appeal under section 58 of the Criminal Justice Act 2003, held the CIE evidence admissible, and ordered the proceedings to resume in the Crown Court.
• Crown Court at Kingston-upon-Hull: His Honour Judge Sampson ruled on 3 February 2012 that the prosecution's proposed expert evidence was inadmissible.