Most UFO cases consist of little more than a witness description of the event. The report form and witness narrative make up the bulk of this data so it is important to assure that it is accurate and complete. This was covered in detail under the "Techniques" Topic, so I won't repeat it here

In the cases of any physical evidence there are some factors that must be considered to insure the evidence is untainted and that a trail is provided to prevent any opportunity to hoax the data. In addition, weather or any conditions which may have altered the evidence should be noted and made a part of the investigation data. This should take into account anything from the time of the occurrence up until the time of your field investigation.

Once the area can be entered safely, it should be done as promptly as possible to prevent either contamination of the sample or possible danger to the witness. Photographic records should be made of the entire area as the search for evidence goes on. If anything is found it should be photographed before any attempt is made to move it. The investigator should have available clean containers which can be sealed to hold any specimens. Any material recovered should be considered hazardous until proven otherwise. The investigator should wear protective gloves when handling any specimens both to protect himself and also to prevent contamination of the sample. The witness retains ownership of the sample unless he specifically says otherwise. Therefore the investigator should give a receipt to the witness before removing any samples for study. If destructive testing is to be performed, the witness must be made aware that his sample may be destroyed before such testing is carried out.

In the case of imprints or tracks, these should be photographed individually and as a group if that is applicable. Plaster casts may be made if conditions warrant it. Soil moisture content and compaction should be tested and noted in order to determine the approximate weight of whatever made the impression. Also take note of any vegetation which has been broken or bent over. Samples may be taken of this as well.

The entire investigation should be logged for tracking purposes. Every person present should initial samples at the time they are sealed. No person should be left alone with the samples at any time until they are sealed. No matter how good the evidence, debunkers will call it a hoax just because the opportunity existed, not because it actually is hoaxed. It's best to have answers when those questions come up. An uninterrupted evidence trail will insure no unanswered questions.