R v Mulhern: Clarifying the Threshold for “Unduly Lenient” Findings in Multi-Count Sexual Offending and the Primacy of Judicial Discretion

1. Introduction

R v Mulhern ([2025] EWCA Crim 757) is a recent decision of the Court of Appeal (Criminal Division) delivered by Lord Justice Edis on 1 May 2025. The judgment arose from an application by the Solicitor General under s 36 Criminal Justice Act 1988 (“CJA 1988”) to refer a Crown Court sentence alleged to be unduly lenient. The offender, Conor Mulhern (aged 51), had covertly filmed a child over several years, carefully curated those images, and also possessed extreme pornography. He pleaded guilty to four counts—voyeurism, possession of extreme pornography, making indecent images of children (Category C), and possession of indecent photographs (Category C)—and received a total of 12 months’ immediate imprisonment (18 months pre-discount).

The prosecution contended that the sentencing judge wrongly treated voyeurism as the principal offence, thereby applying the wrong Sentencing Council guideline. Relying on the higher maximum penalty for making indecent images (five years) and the “production of large numbers of Category C images” category, the Solicitor General argued that the sentence should have been at least two years post-discount and that the Crown Court’s approach was therefore “unduly lenient”. The defence responded that any error in guideline selection made no material difference: even if the indecent-images guideline were primary, the appropriate sentence after discount lay close to the term actually imposed.

2. Summary of the Judgment

The Court of Appeal refused leave to refer; the sentence was not unduly lenient.
While the offending was “extremely serious” and involved grave breaches of trust, the Crown Court judge’s decision to impose immediate custody was pivotal; the precise length, although possibly modest, was within a reasonable margin of discretion.
Even had the judge treated “making indecent images” as the lead offence and started at three years, the one-third guilty-plea reduction would still have produced a sentence within the range capable of suspension; hence, a 12-month immediate sentence was not outside the range of sentences which a judge could properly impose.
The Court emphasised that the s 36 jurisdiction is not to correct any error but only sentences that are “unduly” (i.e., manifestly) lenient; minor or arguable guideline misapplications that yield only a relatively modest disparity will not suffice.

3. Analytical Commentary

3.1 Precedents and Authorities Cited or Implicitly Relied Upon

The judgment itself cites no particular earlier authorities by name, yet several strands of established case-law inform the decision:

s 36 CJA 1988 jurisprudence
Long-standing authorities such as Attorney-General’s Reference (No 4 of 1989) [1990] 1 WLR 41 and R v Cunningham [2001] 2 Cr App R (S) 16 emphasise that a sentence will be increased only when it falls outside the reasonable range. The Court’s repeated use of the phrase “unduly lenient” mirrors these seminal decisions.
Sentencing Council Guidelines
• Voyeurism (revised 2022)
• Sexual Offences – Indecent images of children (revised 2022)
The Court’s discussion contrasts the two sets, highlighting the different maxima (two years vs five) and category starting points.
Credit for Guilty Pleas
The one-third discount derives from s 144 Criminal Justice Act 2003 and the 2017 Definitive Guilty Plea guideline. The Court stresses that any comparative exercise must account for this mandatory reduction.

3.2 Legal Reasoning

“…even if the Solicitor General’s submissions are right, the sentence after discount lay within a range which could lawfully be suspended.” — Lord Justice Edis, para 16

The Court’s chain of reasoning can be broken into four sequential steps:

Error Identification
It accepted for argument’s sake that the judge may have treated voyeurism, a two-year-maximum offence, as the primary compass when the more serious image-making count (five-year maximum) arguably should have been leading. Yet the Court deliberately did not decide the point because it was immaterial to the outcome.
Counterfactual Sentencing Exercise
Applying the Solicitor General’s proposed starting point (three years), the Court deducted one-third for the guilty plea, arriving at two years. Two years, under modern practice, can be suspended (Criminal Justice Act 2003, s 189), showing that the critical question was not maximum exposure but whether immediate custody of meaningful length was imposed.
Assessment of “Unduly” Lenient Standard
The Court reiterated that the s 36 test is a high one. A sentence is “unduly” lenient only when no reasonable judge, applying the relevant guideline and factors, could have passed it. The difference between a 12-month term and, say, a 16- or 24-month term was “relatively modest”, falling short of that threshold.
Public Protection and Deterrence
Emphasis was placed on the immediacy and visibility of the custodial penalty: custody was inevitable, reputational consequences severe, and notification/ancillary orders stringent. Those elements collectively satisfied the aims of punishment and deterrence.

3.3 Impact of the Decision

This ruling clarifies—and slightly tightens—the boundaries of s 36 references in the context of sexual offending comprising multiple guideline-driven counts:

Guideline Misclassification ≠ Automatic Undue Leniency – A mere argument that the wrong guideline was treated as primary will not necessarily succeed; the applicant must show the error produced a sentence outside any reasonable bracket.
Focus on Custody Modality Over Term Length – In borderline cases, whether custody is immediate may be more determinative than precise duration when assessing undue leniency.
Judicial Discretion Preserved – The Court signals reluctance to micro-manage sentencing where the trial judge engaged with aggravating/mitigating factors and landed on a defensible outcome.
Strategic Advice to Prosecutors – The Solicitor General (and CPS) should weigh carefully whether modest sentence uplifts justify invoking s 36; the resource-intensive appellate referral route will be reserved for stark departures.

4. Complex Concepts Simplified

Unduly Lenient Sentence (ULS): A sentence is “unduly” lenient only where it falls outside the range that any reasonable judge could impose, not merely because it is lower than the appellate court might have chosen.
s 36 Criminal Justice Act 1988: Allows the Attorney General or Solicitor General to ask the Court of Appeal to increase a Crown Court sentence they believe is unduly lenient.
Voyeurism vs. Making/Possessing Indecent Images: Voyeurism (s 67 SOA 2003) criminalises covert observation for sexual gratification; maximum two years. Making indecent images (s 1 PCA 1978) often attracts higher maxima (five years) because it inherently involves child sexual exploitation imagery.
Guilty-Plea Reduction: Under s 144 CJA 2003 and the 2017 guideline, a plea at the earliest reasonable opportunity usually earns a one-third discount from the “appropriate” sentence.
Suspended Sentence Range: Custodial terms of two years or less may be suspended (s 189 CJA 2003) if the judge assesses that immediate custody is not necessary and community requirements can meet sentencing objectives.

5. Conclusion

R v Mulhern cements an important practical principle: for a sentence to be revised upward under s 36 it must not simply be arguably low or based on an imprecise guideline choice, but demonstrably outside the spectrum of reasonable sentences. The Court’s approach fortifies trial-level discretion, emphasises proportionality between the error alleged and the remedy sought, and implicitly counsels restraint in bringing ULS references where only a modest uplift could be justified. For practitioners, Mulhern signals that the pivotal questions on a ULS reference are (i) the breadth of the sentencing range once all factors are assessed, and (ii) whether the impugned sentence truly lies beyond its limits. The decision thus reinforces the appellate court’s role as guardian against manifest injustice rather than appellate micro-sentencer.