PROOF BEYOND REASONABLE DOUBT DEMANDS THAT UNWAVERING EXACTITUDE BE OBSERVED IN ESTABLISHING THE CORPUS DELICTI - THE BODY OF THE CRIME WHOSE CORE IS THE CONFISCATED ILLICIT DRUG.

     Thus, every fact necessary to constitute the crime must be established. The chain of custody requirement performs this function in buy-bust operations as it ensures that doubts concerning the identity of the evidence are removed. As a method of authenticating evidence, the chain of custody rule requires that the admission of the exhibit be preceded by evidence sufficient to support a finding that the matter in question is what the proponent claims it to be. It would, thus, include a testimony about the every link in the chain, from the moment the item was seized to the time it was offered in court as evidence, such that every person who handled the same would admit as to how and from whom it was received, where it was and what happened to it while in the witness' possession, the condition in which it was received and the condition in which it was delivered to the next link in the chain. The same witnesses would then describe the precautions taken to ensure that there had been no change in the condition of the item and no opportunity for someone not in the chain to have possession of the same. It is from the testimony of every witness who handled the evidence from which a reliable assurance can be derived that the evidence presented in court is one and the same as that seized from the accused. Due to the procedural lapses pointed out above, serious uncertainty hangs over the identification of the seized shabu that the prosecution introduced into evidence. In effect, the prosecution failed to fully prove the elements of the crime charged, creating a reasonable doubt on the criminal liability of the accused. (People of the Philippines, vs. Erlinda Capuno Y Tison, G.R. No. 185715 January 19, 2011, Brion, J.).