The steps set forth in §§ 18.2-268.2 through 18.2-268.9 relating to taking, handling, identifying, and disposing of blood or breath samples are procedural and not substantive. Substantial compliance shall be sufficient. Failure to comply with any steps or portions thereof shall not of itself be grounds for finding the defendant not guilty, but shall go to the weight of the evidence and shall be considered with all the evidence in the case; however, the defendant shall have the right to introduce evidence on his own behalf to show noncompliance with the aforesaid procedures or any part thereof, and that as a result his rights were prejudiced.