Conspiracy to Supply Drugs Investigations

Last reviewed: September 2026

What must the prosecution prove in a drug conspiracy?

A conspiracy allegation is not simply an allegation that several people knew one another or were involved in the same environment. The prosecution must prove the alleged criminal agreement and the defendant’s participation in it. The scope, period, object and participants therefore matter.

Under section 1 of the Criminal Law Act 1977, the prosecution must prove an agreement with at least one other person that a course of conduct would, if carried out as intended, necessarily amount to or involve the drug offence alleged. The conspiracy is complete when the agreement is made: the prosecution does not have to prove that a further act was carried out in pursuance of it. That makes the evidence said to prove entry into the agreement—not simply later association—critical.

In supply cases, prosecutors may use a conspiracy count where the evidence is said to show overall criminality but individual acts of supply are difficult to isolate. The defence should still test what conduct belongs to which person and whether the evidence proves agreement rather than mere association.

Presence is not the same as participation

Being present in a house, vehicle, group chat or social circle does not by itself prove participation in a conspiracy. The case against each defendant should be separated: what did they know, what did they agree to do, what acts are attributed to them and what independent material supports that inference?

Where drugs, cash or devices are found in shared locations, attribution remains important. Access, ownership, control, fingerprints or DNA, passwords, communications and the accounts of other occupants may all affect the analysis.

Substantive supply and PWITS allegations inside a conspiracy case

A conspiracy case may also include substantive supply or possession-with-intent allegations. Quantity, packaging, cash, scales, phones and messages may be relied on, but each item should be connected to the defendant and considered in context rather than treated as automatic proof of supply.

The defence should test both the underlying facts and the inference drawn from them. If the prosecution says an item is evidence of dealing, the question is why, and whether there is a credible alternative explanation supported by other material.

Define the alleged agreement

The defence should force clarity on the prosecution theory: when did the alleged agreement begin, what drugs or activity did it concern, who were the alleged parties, what was this defendant’s role, and which acts or communications are said to prove entry into the agreement?

Not every defendant must have the same role, but the prosecution still has to prove knowing participation in the alleged agreement. Friendship, family connection, travel or contact with another suspect does not by itself establish a criminal conspiracy.

Phones, encrypted messages and attribution

Phone evidence is often central. The first question is who used the device, SIM, account or handle at the relevant time. The second is what the messages actually mean. The third is whether the prosecution has presented the complete thread and surrounding data rather than selected extracts.

Location data, photographs, contacts, app data and call patterns may also be used to build the alleged network. Defence review should compare those records against the prosecution chronology and identify material that contradicts attribution, presence, role or timing.

Cash and financial evidence

Cash can be relied upon as circumstantial evidence, but it must be placed in context. Legitimate income, withdrawals, business activity, gifts, savings and other sources may be relevant. In larger cases investigators may analyse bank accounts, transfers, cryptocurrency or alleged unexplained wealth. Financial evidence should be reconciled rather than answered with broad assertion.

Searches of homes, vehicles and phones

Drug investigations frequently involve searches under warrant or statutory police powers. The defence should obtain and examine the record of the search, the basis for seizure and the continuity of exhibits. Where the legality or execution of a search is material to the case, the relevant power and circumstances may need separate analysis.

If a phone is seized, investigators may retain it for examination. The status of the download, the scope of extraction and the need for continued retention can all be relevant to case management and disclosure.

Forensic and expert evidence

Laboratory evidence may establish the nature and purity of a substance. Other expert evidence may address valuation, patterns said to indicate supply, digital material, cell-site data or financial analysis. Expert evidence should be tested for methodology, assumptions and whether the conclusion actually follows from the underlying facts.

Alleged hierarchy, role and exploitation

Prosecution cases may assign defendants roles such as organiser, controller, courier, runner or street dealer. Those labels can affect both liability and sentence, but they should be tested against the actual communications, movements, financial evidence and decision-making attributed to the individual.

Where there are indicators of exploitation, coercion or modern slavery, that can require specialist consideration. Such issues are fact-sensitive and should be raised carefully with the defence team rather than assumed.

Police interview strategy

Drug investigations can involve limited police disclosure before interview and extensive digital material that has not yet been reviewed. Interview strategy should therefore be evidence-led. The solicitor should understand what is alleged, what material has been disclosed, what the client can reliably address and whether further evidence is likely to emerge.

A full-comment interview, prepared statement, selective answer or silence each carries consequences. There is no universally correct approach. The right strategy depends on the known evidence, the client’s account and the legal risks at that stage.

Pre-charge strategy in conspiracy investigations

Where the investigation remains open, focused representations may be appropriate if the alleged agreement is overstated, attribution is weak, messages have been misread, chronology is inconsistent, legitimate financial or travel evidence is missing, or a reasonable line of enquiry could materially change the charging assessment.

Representations are strongest when they engage with the actual prosecution theory and evidence. They should not simply repeat the interview account in longer form.

After charge: Magistrates’ Court and Crown Court

The route after charge depends on the offence and seriousness. More serious supply, production and conspiracy allegations are commonly dealt with in the Crown Court. Preparation may involve extensive digital schedules, expert evidence, disclosure review and analysis of co-defendant cases.

Confiscation and POCA

A criminal conviction can be followed by confiscation proceedings under the Proceeds of Crime Act 2002. The financial case may be complex and separate from the trial issues. Benefit, available amount, assets, third-party interests and enforcement can require detailed documentary work. Our practice includes POCA and financial-crime issues as well as the underlying prosecution.

Sentencing considerations

Where there is a guilty plea or conviction, sentence can depend on the nature of the drug, quantity, role, culpability, harm and personal circumstances, together with any aggravating and mitigating factors. The court’s assessment of role should be based on evidence. It should not be accepted automatically because of the way the prosecution describes the case.

Funding

Theodorous holds a Legal Aid Agency criminal contract and can advise on public funding where available. We also undertake privately funded drug cases, including investigation-stage work, pre-charge representations, complex digital review and Crown Court preparation.