Observation responses are those which a witness or potential witness gives based on empirical information. Such information is a collection of personal instances of an event, of witnessing the actions of others, and of the appreciation given to things that are obvious. These types of responses are often objective because they are based on factual and concrete things that can be corroborated provided that the witness is telling the truth. An observation response is elicited with a direct question in the hopes of getting a direct answer that can be corroborated later on in the investigation.
For example: when an attorney or investigator asks about observable behaviors of other people, the witness should respond exactly with what they experienced and saw with their own eyes. No opinions, no personal thoughts, nor indications of bias should be allowed as what was seen was factual.
Inferential responses are those made after deductive and inductive critical thinking has formulated an opinion or a hypothesis of something that has been witnessed. With inferences, the difference is the fact that an external factor drives the individual to use emotion in favor, or against something and, as a result, ideas might be formed regarding in issue.
For example, in observation responses a person will say what they saw someone else do or say. An inferential response will indicate what the witness thinks that the observation might mean. This is why it is so important to keep the two separated.