Every new officer makes mistakes. The ones who progress well are not the ones who make no mistakes — they are the ones who identify errors quickly, understand why they occurred, and build habits that prevent them from recurring. This guide covers the most common first-year errors across the key areas of frontline policing: cautions, statements, search grounds, and exhibit handling. It is written for officers in their probationary period, but the habits described here are relevant throughout a career.
Caution Wording
The caution is fundamental to the lawful administration of a police interview and the admissibility of anything said during it. Officers who get the wording wrong — or who deliver it without understanding what it means — create problems that can undermine prosecutions.
The full caution used in England and Wales is: *"You do not have to say anything. But it may harm your defence if you do not mention when questioned something which you later rely on in court. Anything you do say may be given in evidence."*
The most common errors:
Paraphrasing. Some officers, nervous about the length of the caution, shorten it. "You have the right to remain silent, anything you say can be used against you" is not the caution used in England and Wales — it is the American Miranda warning from television. The actual caution has three specific elements: the right to silence, the adverse inference warning, and the admissibility warning. All three must be present and correctly worded.
Not explaining it. Under PACE Code C, if a person does not appear to understand the caution, you must explain it in your own words. "Do you understand the caution?" followed by "yes" is not sufficient if it is obvious they did not understand it. Take the time to explain what it means, particularly with vulnerable adults, young people, or people with limited English.
Cautioning at the wrong time. The caution should be given at the point of arrest, before interview begins, and after a significant break in interview. Officers sometimes forget to re-caution after a break, or caution too early in a scenario before the grounds for arrest are established. Know when the caution is required and be deliberate about it.
Voluntary attendance vs. arrest. If a person attends the station voluntarily to assist with enquiries, they are not under caution unless and until they are arrested or grounds for administering a caution arise. Cautioning a voluntary attendee prematurely can create confusion about their status.
The solution is practice. Verbalise the full caution out loud in training. Know it so thoroughly that you could recite it under pressure, on a dark street, in the rain, at 3am.
Statement Writing
A witness statement (MG11) is a legal document. It can be used as evidence in court, challenged by defence solicitors, and scrutinised in detail by a judge. Poor statement writing is one of the most common sources of both complaint and unsuccessful prosecution.
First-person, past tense, chronological order. Your statement should read as a clear, chronological account of what you personally observed and did. "I arrived at the address at approximately 0230 hours. I saw a male I now know to be John Smith standing in the doorway. He appeared to be holding an object in his right hand." Not: "Upon arrival the male was observed with an object."
Do not write conclusions — write observations. "I could smell cannabis" is admissible. "He had obviously been smoking cannabis" is not — you cannot establish that from smell alone. "The defendant appeared intoxicated" is borderline — say "his speech was slurred, his eyes were glazed and he was unsteady on his feet" and let the court draw the conclusion. Describe what you saw, heard, and smelled. Do not characterise.
Do not leave gaps. If there is a gap in your narrative — you went back to the station, completed paperwork, and then returned to the scene — include that. Defence solicitors look for gaps and use them to suggest that events during the gap are being concealed.
Write contemporaneously. Ideally, notes are made at the time or immediately after. Statements written hours or days later from memory will contain errors and omissions that cross-examination will exploit. Use your pocket notebook at the scene. Write the formal statement as soon as possible afterwards. Note that you made pocket notebook entries at the time and refer to them.
Exhibit labels. If you reference an exhibit in your statement, the exhibit number must match exactly. "I seized a knife which I labelled exhibit JD/1" requires that the exhibit label reads JD/1, signed by you. Mismatched exhibit references are a surprisingly common error that defence solicitors highlight as evidence of disorganised record-keeping.
Search Grounds: Forming Them, Articulating Them
Stop and search errors are covered in detail in a separate article, but the fundamental mistake new officers make is exercising a search power because they have a feeling about someone, then trying to construct grounds afterwards.
Reasonable grounds for a Section 1 PACE search must be specific and articulable. Before you approach anyone, ask yourself: "What would I write in the search record right now?" If your answer is "he looked suspicious" or "she was acting nervously", you do not have grounds. If your answer is "I saw a handle consistent with a bladed article protruding from his right jacket pocket", you do.
The test is objective. It is not about what you believe — it is about what a reasonable officer in your position would believe, based on specific facts. Get into the habit of asking yourself that question before every search.
New officers also struggle with Section 23 Misuse of Drugs Act searches. The smell of cannabis is sufficient for reasonable suspicion, but it must be specifically the person you intend to search — not just a general smell in the area. "I could smell cannabis emanating from the direction of the male" is better than "I could smell cannabis in the area."
After a search, complete the search record immediately. Do not wait until end of shift. The search record is a live legal document — get it right at the time.
Exhibit Handling
Poor exhibit handling has derailed prosecutions. The principles are not complicated, but they require discipline.
Label at the point of seizure. The moment you seize an item, it becomes an exhibit and must be labelled. Your exhibit reference is your initials plus a sequential number — if you are officer JD and this is your third exhibit today, it is JD/3. Write the reference on a label attached securely to the item (in a sealed bag where appropriate), note it in your pocket notebook at the time, and reference it in your statement.
Document the continuity. An exhibit must have an unbroken chain of custody from seizure to court. Every time the exhibit changes hands — to another officer, to the custody sergeant, to the exhibit store, to the analyst — that transfer must be documented. If you cannot account for where your exhibit was from the moment you seized it to the moment it was examined, the defence will challenge it.
Package correctly. Wet items (blood, urine, biological samples) cannot be sealed in plastic bags — they will degrade and contaminate. Use paper bags. Sharp items must be packaged to protect handlers. Drug exhibits should be weighed and sealed appropriately. Ask your custody sergeant or exhibits officer if you are unsure.
Do not open sealed exhibits. Once an exhibit is sealed and labelled, do not open it. If you need to view it again, the packaging must be documented and re-sealed. Exhibits that show signs of having been opened without documentation are vulnerable to challenge.
Building Good Habits
The errors above share a common theme: they occur when officers work from memory, cut corners under pressure, or prioritise speed over accuracy. The solution is not to slow down — it is to build habits so embedded that accuracy is automatic even at speed.
The officers who handle the first-year transition best are typically those who:
- Carry their pocket notebook and write in it at every significant moment, not at the end of the shift - Ask questions — of their tutor constable, their sergeant, their custody sergeant — rather than guessing - Accept correction gracefully and implement the feedback immediately rather than defensively - Treat every MG11, every exhibit label, every search record as though it will be read by a defence barrister — because eventually, some of them will be
Mistakes in your probationary period are expected and survivable. What supervisors and colleagues notice is how you respond to them. Officers who acknowledge errors, understand why they occurred, and visibly adjust their practice are the ones who emerge from probation with a reputation as people worth investing in. The habits you build in your first year will shape your practice for the rest of your career — build good ones deliberately.