Final answer:
The prosecution's introduction of evidence without prior disclosure to the defense violates the Sixth Amendment, as it interferes with the right to be informed of evidence and to prepare a defense.
Step-by-step explanation:
In a murder trial, if the prosecution denies having specific evidence and later presents it without prior notice to the defense, this constitutes a violation of the Sixth Amendment. This Amendment guarantees the accused the right to be informed of the evidence against them in a trial to prepare an adequate defense. By not disclosing this demostrative evidence beforehand, the prosecution undermines the defense's ability to effectively cross-examine witnesses and challenge the admissibility of the evidence, which could be grounds for an appeal or a mistrial, depending on the circumstances of the case and the decision of the presiding judge.