In Applying the Federal Rule 901 (Requirement of Authentication or Identification)

In applying the Federal Rule 901 (Requirement of Authentication or Identification) , federal courts have:

A) refused to admit real evidence if a continuing chain of custody is not clear.
B) been fairly consistent in allowing real evidence to be admitted, even if the chain of custody is not clear, where the items have been in official custody and there is no affirmative evidence of tampering.
C) ruled that the prosecutor does not have to introduce evidence to show that it is improbable that the item might have been contaminated or been subjected to tampering.
D) held that there is a presumption that federal officers have not discharged their duties properly but that this presumption may be overcome.