Collecting samples

Representative samples - analysts work with samples, these must be representative- there should be enough of the sample to give a picture of the whole item.the sampling methods depends on the nature of the sample.

Preservation of samples - important tp prevent any changes or deterioration of the sample.some samples have to be analysed immediately.otehrs can be stored under suitable conditions.

avoiding contamination - crime scene investigators wear protective clothing and put all samples into sealed bags or botles to avoid contaminating samples.they may have to appear in court to give evidence about possible routes of contamination.

avoiding tampering - known fot urine samples taken for drug testing.it is important to have chain of custody' evidence and tampeer-proof seals, so it can be shown exactly who had access to the samples