The Liam Allan Case: What Every Investigator Must Learn About Reasonable Lines of Enquiry
- Cognition Training and Consultancy
- Feb 27
- 6 min read
Updated: Mar 3
Overview of the Liam Allan Case (2017)
The Liam Allan case became one of the most significant disclosure scandals in modern UK criminal justice. Allan, a 22‑year‑old student, was charged with rape and sexual assault, following an allegation made by a woman with whom he had been in a relationship.. The case collapsed in December 2017 when previously undisclosed digital evidence—thousands of text messages—contradicted the allegations.
The CPS abandoned the prosecution at Croydon Crown Court, triggering a joint review by the Metropolitan Police and CPS that confirmed serious disclosure failings and clear breaches of CPIA duties.
Legal scholars described the case as a “near miss” miscarriage of justice, exposing systemic problems in police disclosure practice, investigative culture, and digital evidence handling. For workplace investigators, the lessons are striking: early‑stage disclosure failures, unchecked bias, and poor evidence management can distort any investigation—criminal, civil, or organisational—and place innocent people at risk of unfair outcomes.
Background: Liam Allan and the Complainant
Liam Allan was a 22‑year‑old criminology student living in south London. He was, by all accounts, an ordinary university student balancing studies, friendships, and part‑time work and no previous contact with the criminal justice system.
He and the complainant had been in a casual sexual relationship, communicating frequently by text message and social media. Their interactions were typical of many young adults: informal, sometimes intense, and heavily reliant on digital communication.
The complainant later made allegations of rape and sexual assault to the police against Allan.
The Police Investigation
When police arrested Liam Allan in January 2016, the investigation entered its most formative stage. This is the point at which early decisions—about what evidence to gather, what to prioritise, and what to dismiss—shape the entire trajectory of a case. For Allan, those early decisions would prove critical.
After the arrest, officers seized devices and began reviewing the complainant’s account. As part of standard procedure, they downloaded the complainant’s mobile phone, capturing tens of thousands of messages exchanged over months. These messages documented the tone of the relationship, the expectations between the two, and the context surrounding their interactions.
Under the CPIA, investigators were required to pursue "reasonable lines of enquiry", that might support or undermine the allegation. The digital material should have been central to that process.
Instead, investigators concluded that the phone data contained “nothing of relevance.” This assessment was recorded and relied upon, despite the sheer volume of material and its obvious potential significance. That single decision shaped the direction of the enquiry. Interviews, case reviews, and evidential assessments all proceeded on the assumption that the digital evidence had been properly examined and found insignificant.
From that point forward, the investigation narrowed. Officers focused on building a case around the complainant’s account rather than testing it. Reasonable lines of enquiry that might have challenged the allegations were not pursued. Supervisory oversight did not question the early assumptions.
After spending several months on police bail, Allan was charged with six counts of rape and six counts of sexual assault, clearly very serious charges, which if convicted would attract a significant custodial sentence.
For workplace investigators, this phase of the Allan case illustrates several familiar risks:
Early assumptions can harden into “facts” if they are not actively challenged.
Digital evidence requires deliberate, structured review, not a cursory glance.
CPIA‑style thinking—seeking both inculpatory and exculpatory material—is essential in any investigative setting.
Oversight matters; unchecked decisions at the start can distort everything that follows.
By the time the case reached court, the investigation had been shaped by a series of early misjudgments that went uncorrected. The seeds of the disclosure failure were planted at the very beginning.
The Disclosure and Court Process
After charge, the case file was passed between officers and reviewed by the CPS. However, the initial conclusion—that the digital download contained “nothing of relevance”—remained unchallenged. This meant:
the complainant’s account became the central pillar of the case
digital evidence was treated as peripheral
reasonable lines of enquiry that might undermine the allegation were not pursued
the defence was repeatedly told there was no unused material of value
This narrowing is a classic example of confirmation bias: once a theory of the case is formed, investigators unconsciously seek information that supports it and overlook material that contradicts it.
There were multiple missed opportunities for corrective oversight during this phase. Supervisors and reviewing lawyers had several chances to question the lack of digital evidence review—something that should have been obvious given the centrality of the phone material.
Under CPIA, they were required to ensure:
all relevant material had been examined
unused material schedules were accurate
enquiries that might point away from guilt had been identified and considered
None of these checks identified the gap. The assumption that the phone messages were irrelevant was simply carried forward.
By late 2017, Allan had been on bail for nearly two years. The case continued to move through the system based on incomplete evidence review. Disclosure schedules were prepared, but they reflected the original flawed assessment. Defence requests for digital material were met with assurances that nothing useful existed.
This created a dangerous illusion of completeness: the investigation appeared thorough on paper, but the foundation was unsound.
The Case Reaches Croydon Crown Court
As the trial approached, the defence continued to request access to the digital evidence. Each time, they were told that the material had been reviewed and that nothing useful existed. This created a false sense of completeness. On paper, disclosure obligations appeared to have been met. In reality, the most important evidence in the case had never been examined.
In December 2017, nearly two years after his arrest, Allan’s trial began at Croydon Crown Court. The prosecution opened the case based on the complainant’s account and the assumption that no digital evidence undermined it. The defence, still concerned about the missing phone material, renewed their request for the full download.
This time, the prosecution agreed to provide it.
When the defence barrister received the full digital file, she worked through the night reviewing tens of thousands of messages. What she found fundamentally changed the case:
messages expressing sexual interest in Allan
messages contradicting the allegations
messages showing frustration when he did not respond
messages that directly undermined the prosecution’s narrative
These were not marginal or ambiguous. They were central to understanding the relationship and the allegations. Their absence from the disclosure schedule represented a clear breach of CPIA duties.
The Collapse of the Case
The next morning, the prosecution offered no evidence.
The judge halted the trial immediately, describing the situation as a “disaster” and warning that the justice system had come dangerously close to convicting an innocent man. The CPS and Metropolitan Police launched a joint review, which confirmed:
the digital evidence had not been properly examined
disclosure duties had been breached
oversight mechanisms had failed
the investigation had been shaped by early assumptions rather than full evidence review
Why This Moment Matters for Workplace Investigators
Because this is a criminal case, investigators working in this area should not only know the Allan case, but ensure their own investigations reflect its CPIA lessons.
Although the Allan case sits within criminal justice, the underlying investigative failures translate directly to organisational and workplace settings. The themes—confirmation bias, incomplete evidence review, poor documentation, and weak oversight—are universal risks.
Key lessons that apply to workplace investigations
Early assumptions must be tested, not trusted.
The Allan case shows how an early belief (“nothing relevant on the phone”) shaped an entire investigation. Workplace investigators face the same risk when initial accounts or impressions go unchallenged.
Digital evidence must be reviewed systematically.
Modern cases—whether criminal or workplace—often hinge on messages, emails, and metadata. Volume is not an excuse for avoidance.
Disclosure is an ongoing duty.
In workplace settings, this means sharing relevant material with all parties, documenting what has been reviewed, and ensuring transparency throughout.
Oversight must be active, not administrative.
Supervisors should probe early decisions, ask what has been reviewed, and ensure that alternative explanations have been considered.
Investigators must pursue lines of enquiry that both support and challenge the allegation.
This CPIA principle is directly transferable to workplace investigations. Fairness requires balance.
Documentation protects the process.
Clear records of what was reviewed, why decisions were made, and how evidence was interpreted help prevent disputes and strengthen defensibility.
Closing Reflections: The Essential Takeaway
The Liam Allan case showed how an investigation can unravel when early assumptions go untested and key evidence is not properly reviewed. For nearly two years, the enquiry relied on the belief that the complainant’s phone held “nothing of relevance,” despite clear CPIA duties to examine and disclose material that might support or challenge the allegation. When the messages were finally reviewed at trial, they revealed a completely different picture—one that should have been identified at the start.
The national fallout confirmed wider issues in disclosure culture, digital capability, and oversight. But the relevance extends far beyond criminal justice. Any investigation can drift off course when evidence is filtered through assumptions rather than examined in full.
For workplace investigators, the core message is simple: fairness depends on reviewing all relevant material, challenging early decisions, and treating disclosure as a safeguard, not a formality. When investigators stay curious, document their reasoning, and commit to transparency, they create processes that are both defensible and genuinely fair.
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