Obtaining evidence using section 20 powers

Powers of inspectors

1. Inspectors appointed by an enforcing authority under section 19 HSWA have extensive powers to carry into effect any of the relevant statutory provisions.1 The powers set out in sections 20(2) and 25 HSWA include powers to:

  • Enter any premises which inspectors think it necessary to enter for the purposes of enforcing HSWA and the relevant statutory provisions. They may only enter at a 'reasonable time', unless they think there is a situation which may be dangerous.2 If they have reasonable cause to apprehend serious obstruction, they may take a police officer;;3
  • Order areas to be left undisturbed,4 take measurements, photographs and recordings,5 take samples6 and take possession of, and carry out tests on, articles and substances that appear to have caused (or be likely to cause) danger;7
  • Require the production of, inspect and take copies of relevant documents;8
  • Require anyone they think might give them relevant information to answer questions and sign a declaration of the truth of the answers;9
  • Require facilities and assistance to be provided;10 and
  • Seize and make harmless (by destruction if necessary) any article or substance which they have reasonable cause to believe is a cause of imminent danger of serious personal injury11.

2. Inspectors are also given any other power which is necessary for the purpose of carrying into effect the relevant statutory provisions.12

Discretion and impact of the Human Rights Act

3. These powers are wide-ranging and it is a matter for your discretion as to whether, and in what circumstances, you exercise them. You may be able to obtain any evidence you require voluntarily, without recourse to your powers.

4. As a public authority, HSE must act in a way that is compatible with the European Convention on Human Rights (ECHR).13 You should be mindful that use of your powers may interfere with the human rights of a person (including a corporate body), such as the right to respect for a private life, home and correspondence, and the right to peaceful use of personal property.

5. Any use of your powers must be necessary, justified and proportionate: see Judge over HSE's shoulder for further guidance. You should record any decision to exercise your powers, together with the reasons for it.14 In major investigations, it may be appropriate to record the decision and supporting reasons in the key decision log.

6. Whenever you use or seek to use any of your powers, you must produce your warrant if asked.15

Consequences of obtaining evidence improperly

7. If you obtain evidence improperly, for example by exceeding any of the powers set out in HSWA, by failing to follow a PACE Code when required to do so, or by acting in a way that is incompatible with the ECHR, a court may rule that the evidence would have such an adverse effect on the fairness of the proceedings that it should not be admitted in evidence. Any unjustified use of your powers could also provoke a civil action for damages. 15 If the impropriety is sufficiently serious, it may form the basis of an abuse of process argument.


8. You have the power to require any person to produce any books or documents required to be kept under any of the relevant statutory provisions, and any other books or documents which are necessary for you to see for the purposes of your investigation. 16 This would include any document which assists you in deciding whether you should prosecute.

9. You have the power to inspect and take copies of such documents. If you do not take a copy, you should carefully note the contents in your notebook. Section 20(2)(k) does not give you the right to seize original documents. If you need to do this, you should refer to the section on 'Original documents or copies?'.

10. Where you do not have access to copying facilities on site, you may need to remove the original for copying. In such cases, you should give a responsible person a notice on form LP24, identifying the document and stating that you have taken possession of it using your s.20 powers 17 but will return it as soon as the necessary copy has been made. You should record in your notebook as to why you took the original for copying and also note when you returned the original.

Reference to new physical evidence obtained

11. You may have to go back and ask a witness about documents or objects that you have subsequently obtained. If you have already taken a statement from the witness, you may have to take a further statement to record their response.

12. For example, where a document has been produced by a potential defendant to show the steps taken with regard to safety, you should refer these to any witness who should have been aware of those steps or protected by them, in order to discover whether they knew of the document and whether such steps were in fact taken.

13. You may also wish to ask your expert to comment, for example, on whether measures had been taken to reduce the risk so far as was reasonably practicable.

Obtaining information in writing

14. Section 20(2)(j) allows inspectors to seek and obtain information. In normal circumstances, you will seek to obtain the information by interviewing a person and taking a witness statement. However, if this is not possible or appropriate, the section entitles you to seek and, if necessary, require information in writing, for example by correspondence. 18

Documents from computers

15. Generally, it is not the computer itself which is evidence in a case, but the information held within the computer. In straightforward cases, if you require information which you know is held on the computer, you should ask the duty holder to print out the information for you, using section 20(2)(m) powers.

16. You should ask the duty holder if the computer is working properly as far as s/he knows. In less straightforward cases (for example, where you need to prove that an entry was falsely dated, or in cases where the duty holder is not cooperative), you may need to take a computer expert with you, using section 20(2)(c) powers, who can examine it and extract any necessary information.

17. Greater interference with a computer, such as seizure, will need to be carefully considered. Whether section 20(2)(m) permits interference in any particular case will depend on whether use of the power would be necessary, justified and proportionate. Alternative courses of action should be considered; for example, in an exceptional case, where a large amount of relevant material was known to be held on computer, you may consider using your power under s.20(2)(m) to direct a computer expert to 'image' the computer's hard drive and take the image away to obtain the necessary material. This would reduce the impact of your actions on the duty holder as the computer would be unavailable for the minimum length of time. In each case, however, you would also need to consider how to preserve, and ensure continuity of, any evidence.

18. Requests for specialist help should be done through the normal channels in your Directorate/Division.

Power to leave undisturbed

19. You have power to direct that the premises, or any part of them, or anything in them, be left undisturbed for so long as is reasonably necessary for the purpose of your investigation. 19 This power may be exercised, for example, where:

  • the configuration of the site or machine at the time may be essential for determining physical evidence;
  • where you decide that investigation by your expert is necessary; or
  • where you need to return with specialist measuring or testing equipment.

20. You may be able to arrange informally with a duty holder that the item or area is left undisturbed, but where you are not certain that s/he will comply, you should issue a formal notice. A formal notice to leave undisturbed should be in writing and include:

  • reference to s.20(2)(e);
  • a fixed period of time during which no disturbance should be made. This can later be extended if necessary.

21. You should not rely on the fact that an employer is going to obtain a report on equipment, because that report may be the subject of legal professional privilege and therefore may not be disclosed to you. "Legal professional privilege" is considered in more detail later in this section.

Taking possession of an article/substance

22. You have power to take possession of any article or substance which appears to you to have caused, or to be likely to cause, danger to health or safety in order to examine it, ensure that it is not tampered with, or ensure that it is available for evidence in a prosecution. 20

23. When you do so, you must leave a notice with a responsible person at the premises or, where this is impracticable, fix the notice in a conspicuous position:

  • giving sufficient details of the article to identify it; and
  • stating that you have taken possession of it using your s.20(2)(i) power. 21

24. Unless it is not practicable, before taking possession of an article or substance using your s.20(2)(i) power, you should leave a marked sample of the substance or article with a responsible person on the premises. 22


25. You have power to take samples of any articles or substances and to take atmospheric samples. 23 The occupier or other responsible person must always be informed of the intention to take samples for analysis.

26. When the sample has been collected it should be divided into three parts. One part should be given to the occupier, another sent for analysis and the third retained by the inspector.

27. Each item must be uniquely identified by a label and recorded, using the proper containers, packing, labels and seals. The labels should state the premises of origin, a description of the sample, a number (if there is more than one sample), the date, and your name and title.

28. Samples (link to sample section within site visits page) are dealt with in more detail in "Expert Evidence".

Analysis and tests

29. You have the power to dismantle, or subject to any process or test, any article or substance which appears to you to have caused, or be likely to cause, danger to health or safety. 24

30. Where any person responsible for the premises from which the article was taken asks to be present when the dismantling or testing is carried out, this should be allowed. 25 You should also contact them if the test will irreversibly alter the article to give them an opportunity to be present.

31. So far as possible, you should retain enough of the item to facilitate further independent tests. If this is not possible, you should video, photograph or otherwise record the test to ensure that the results can be proved in court.

32. You have the power to take such measurements and photographs, and to make such recordings, as you consider necessary to your investigations. 26

Recording actions

33. All the circumstances surrounding the taking of a sample or the taking possession of an article for tests should be noted carefully in your notebook and included in your statement.

Interrelationship of section 20 HSWA and PACE Code B

34. HSWA does not include a power of search and seizure. If you enter premises using your section 20 powers, the Police and Criminal Evidence Act 1984 Revised Code of Practice B on search and seizure does not apply (Code B, paragraph 2.5).

35. However, very rarely, circumstances may arise where, for the purposes of your investigation, you wish to conduct a search. In such circumstances, you could only do so with consent and you would have to follow those provisions of Code B that relate to voluntary searches.

36. These include a requirement that you secure written consent from a person entitled to grant entry to the premises. Before seeking consent, you should inform the person of the purpose of the proposed search, that s/he is not obliged to consent and that anything seized may be produced in evidence.

37. Searches must be conducted at a reasonable hour, only to the extent necessary to achieve the object of the search and with due consideration for the property and the privacy of the occupier. A search record will need to be made setting out the details identified in paragraph 8.1 of the Code. If you consider that a search of premises is necessary in a particular case, you should first seek legal advice.

Legal professional privilege

38. Your powers under section 20 cannot compel the production of documents which are entitled to be withheld on grounds of legal professional privilege. 27

39. There are two types of legal professional privilege: advice privilege and litigation privilege.

40. Legal advice privilege extends to all confidential communications between a lawyer and client that are made for the purpose of giving or obtaining legal advice.28 This can include statements, reports and other information. Legal advice privilege does not cover communications sent to or from a third party.29

41. Litigation privilege extends to documents created for the dominant purpose 30 of existing or contemplated adversarial legal proceedings (such as civil litigation or criminal proceedings but not, for example, investigative inquiries).

42. Litigation privilege attaches to communications between solicitors and expert witnesses, including any written expert report which has been prepared for a dutyholder's solicitor in contemplation of legal proceedings. The expert's opinion on the case may not be privileged, depending on whether that opinion was based on consideration or privileged material or discussions, and there may be occasions where HSE can still call a dutyholder's expert to give oral evidence or put our own questions to them, even if we cannot access their report due to privilege.  If you are considering this, it would be wise to speak to either LAO / your instructed solicitor agent. However, you should also note the requirements relating to disclosure of expert evidence in criminal proceedings: guidance can be found in the section 'Approach to common categories of material', both for investigations commenced before 4 April 2005 and those begun on or after 4 April 2005.

43. The privilege belongs to the client and not the lawyer; a duty holder has the ability to waive any privilege and show you the document in question, for example to assist, or to cooperate with, your investigation. Similarly, a client may choose to waive privilege in order to use the document in evidence.

44. If a company has prepared an incident report, litigation privilege may be claimed if the dominant purpose of creating the document was to obtain legal advice in relation to legal proceedings. An engineer's report, for example, that was obtained for the purpose of deciding whether to contest proceedings (civil or criminal) will be protected by privilege. However, this will not be the case if the report was prepared simply because there had been an incident 31, or to avoid further incidents. In such circumstances, you are entitled to require production of the report if it is necessary for the purposes of carrying into effect any of the relevant statutory provisions. 32


  1. As the Employers' Liability (Compulsory Insurance) Act 1969 ('ELCI') is not a 'relevant statutory provision' under HSWA, inspectors authorised to enforce the provisions of ELCI have the limited powers set out in that Act and the regulations made under it; see [OC 1/8]. Back to reference of footnote 1
  2. Section 20(2)(a). Back to reference of footnote 2
  3. Section 20(2)(b). Back to reference of footnote 3
  4. Section 20(2)(e). Back to reference of footnote 4
  5. Section 20(2)(f). Back to reference of footnote 5
  6. Section 20(2)(g). Back to reference of footnote 6
  7. Section 20(2)(h) and (i). Back to reference of footnote 7
  8. Section 20(2)(k). Back to reference of footnote 8
  9. Section 20(2)(j). The person interviewed may nominate a person to be present but no-one else may be present unless allowed by the inspector. Where an inspector requires a person to answer questions pursuant to this section, the answers given cannot be used in evidence against that person or his/her spouse or civil partner (section 20(7), as amended by the Civil Partnership Act 2004, Schedule 27 Para 49). Back to reference of footnote 9
  10. Section 20(2)(l). Back to reference of footnote 10
  11. Section 25(1). Conditions on the use of this power are set out at s.25(2) and (3). Back to reference of footnote 11
  12. Section 20(2)(m). Back to reference of footnote 12
  13. Section 6 Human Rights Act 1998. Back to reference of footnote 13
  14. See, for example, R (on the application of TB) v Stafford Crown Court [2006] EWHC 1645 (QBD (Admin)): a court (as a public authority) may only order the disclosure of medical records, in breach of confidentiality, if this was proportionate, in accordance with the law and necessary for the prevention of crime, for the protection of health or morals or for the protection of the rights and freedoms of others. When assessing compliance with the ECHR, a court will have regard to how the decision in question was reached. Back to reference of footnote 14
  15. Section 26 empowers HSE to indemnify inspectors. Back to reference of footnote 15
  16. HSWA 1974, s.20(2)(k). Failure to produce a document could give rise to a separate offence under s.33(1)(e). Back to reference of footnote 16
  17. Where taking possession of the original document for copying can be justified in the circumstances of the investigation, you will rely on s.20(2)(m), which gives inspectors 'any other power which is necessary' for the purpose of carrying into effect the relevant statutory provisions. Back to reference of footnote 17
  18. London Borough of Wandsworth v South Western Magistrates Court [2003] EWHC 1158 (Admin). For guidance on interviewing suspects by letter, see Questioning of suspects. Back to reference of footnote 18
  19. HSWA 1974, s.20(2)(e). Back to reference of footnote 19
  20. HSWA 1974, s.20(2)(i). Back to reference of footnote 20
  21. Form LP6. Back to reference of footnote 21
  22. HSWA 1974, s.20(6). Back to reference of footnote 22
  23. HSWA 1974, s.20(2)(g). Back to reference of footnote 23
  24. HSWA 1974, s.20(2)(h). Before exercising this power, you must consult any person you consider appropriate to find out what dangers there may be in dismantling or testing. You should therefore consult your expert, and in some cases, management or technicians at the premises: s.20 (5). Back to reference of footnote 24
  25. HSWA 1974, s.20(4). Although this right does not extend to trade unions, it is good practice not to exclude them if they wish to be present. A person who has a right to be present does not have a right to be represented at the test, but such requests should normally be granted. Back to reference of footnote 25
  26. HSWA 1974, s.20(2)(f). Back to reference of footnote 26
  27. HSWA 1974, s.20(8). Back to reference of footnote 27
  28. Three Rivers District Council & Ors v Governor and Company of the Bank of England [2004] UKHL 48. The advice must be given in a "relevant legal context", where the lawyer is consulted because of his/her professional expertise. Back to reference of footnote 28
  29. The privilege extends to counsel and solicitors, and their clerks and agents. Back to reference of footnote 29
  30. Waugh v British Railways Board [1980] AC 521, HL: it may not be the sole purpose of the document, provided it was the dominant purpose. Back to reference of footnote 30
  31. Lask v Gloucester Health Authority [1991] 2 Med LR 379, CA. Back to reference of footnote 31
  32. HSWA 1974, s.20 (2)(k). Back to reference of footnote 32

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Updated 2020-11-02