The order in which you collect evidence is important; in all cases you should work through each stage, starting with preserving and recording the scene. However, every situation is unique, therefore the way you investigate and collect evidence will depend on the individual circumstances of each case.
Evidence should generally be collected as follows:
If you are investigating an incident, you should identify and obtain evidence from the "witnesses of fact" (i.e. those able to give factual information about what actually occurred, usual work systems and relevant employment issues etc). This will normally be done by taking a statement.
Once you have obtained evidence from the witnesses of fact, you should then seek to identify the underlying causes of the suspected breach(es) by seeking further information. This may involve taking statements from people who hold more senior positions in the organisation under investigation who may not have witnessed the incident. You should avoid seeking information from people who you suspect may have committed an offence as an individual under HSWA and/or regulations, although you may consider an interview under caution. The contents of written documents, assessments, procedures, policies etc may help to inform you as to who may, or may not, be a suspect.
A caution is not necessary when you are asking questions to clarify whether you should have grounds for suspecting someone. For example, you may ask questions to establish someone’s identity, position, or their ownership of a certain vehicle. You should remember, however, that what starts out as exploratory questioning may, as a result of answers given, become questioning about a person’s involvement, or suspected involvement, in a criminal offence. You must then immediately caution the individual who has become a suspect through your questioning.
The final state of the investigation will usually be to speak to those people suspected of having committed an offence. This should be a formal interview under caution. It is HSE policy to give a suspect who has been cautioned the right to consult a solicitor (see ‘Disclosure and redaction’).
If a person who you interviewed under caution ceases to be a suspect and you wish to rely on their evidence, you should inform them and re-interview them as a witness of fact. Alternatively, you may draft a statement from the content of the interview under caution and then ask the individual to sign the statement.