[1] Defendant contends that the trial court erred in failing to require disclosure of the identity of the State’s confidential informant. We do not agree. Defendant is correct in his position *476that the privilege of non-disclosure must give way when the informant’s identity is essential or relevant or helpful to the defense or is essential to a fair determination of the cause. Roviaro v. United States, 353 U.S. 53, 77 S.Ct. 623, 1 L.Ed. 2d 639 (1957); State v. Fletcher and State v. St. Arnold, 279 N.C. 85, 181 S.E. 2d 405 (1971). Furthermore, the State is compelled to disclose the identity of the informant if it appears that he is a participant as opposed to a “mere tipster.” McLawhorn v. North Carolina, 484 F. 2d 1 (4th Cir. 1973). The case before us does not fall within the rule of the cases cited, for defendant has made no showing either that the informant was a participant in the offense or the manner in which the identity of the informant would be essential to his defense. This assignment of error is overruled.
[2] Defendant next assigns error to the failure of the court to quash the bill of indictment which, he contends, is based upon an. unconstitutional statute, G.S. 90-88. Among the several grounds for defendant’s challenge to the constitutionality of G.S. 90-88 is his position that it represents an unauthorized delegation of legislative authority, viz: the authority to define crimes. His specific objection is that G.S. 90-88 empowers the North Carolina Commission of Health Services to add, delete, or reschedule a substance as a controlled substance.
Our Supreme Court addressed the issue of the delegation of legislative authority in the leading case of Coastal Highway v. Turnpike Authority, 237 N.C. 52, 60-61, 74 S.E. 2d 310 (1952) :
“However, it is not necessary for the Legislature to ascertain the facts of, or to deal with, each case. Since legislation must often be adapted to complex conditions involving numerous details with which the Legislature cannot deal directly, the constitutional inhibition against delegating legislative authority does not deny to the Legislature the necessary flexibility of enabling it to lay down policies and establish standards, while leaving to designated governmental agencies and administrative boards the determination of facts to which the policy as declared by the Legislature shall apply. Provision Company v. Daves, supra. Without this power, the Legislature would often be placed in the awkward situation of possessing a power over a given subject without being able to exercise it.
*477Here we pause to note the distinction generally recognized between a delegation of the power to make a law, which necessarily includes a discretion as to what it shall be, and the conferring of authority or discretion as to its execution. The first may not be done, whereas the latter, if adequate guiding standards are laid down, is permissible under certain circumstances. 11 Am. Jur., Constitutional Law, Sec. 234. See also Pue v. Hood, Comr. of Banks, 222 N.C. 310, 22 S.E. 2d 896.
Nevertheless, the legislative body must declare the policy of the law, fix legal principles which are to control in given cases, and provide adequate standards for the guidance of the administrative body or officer empowered to execute the law. ... In short, while the Legislature may delegate the power to find facts or determine the existence or nonexistence of a factual situation or condition on which the operation of a law is made to depend, or another agency of the government is to come into existence, it cannot, vest in a subordinate agency the power to apply or withhold the application of the law in its absolute or unguided discretion, 11 Am. Jur., Constitutional Law, Sec. 234.”
It should be apparent that the General Assembly is not constantly in session, and, therefore, even if its members were all trained chemists and pharmacists, which they are not, it is impossible for them to keep abreast of the constantly changing drugs and medications and their inherent dangers which appear on the pharmaceutical scene. G.S. 90-88 does not delegate the authority to define crimes; rather it is a delegation of authority to “find facts or determine the existence or nonexistence of a factual situation or condition on which the operation of a law is made to depend.” Coastal Highway v. Turnpike Authority, supra, at 61. An examination of the statute reveals that the Legislature has imposed guidelines upon the rescheduling of controlled substances that are more than adequate within the purview of Coastal Highway, supra. We have carefully reviewed defendant’s other attacks on the constitutionality of G.S. 90-88, and we find them to be without merit.
[3] Defendant assigns error to the admission into evidence of items seized pursuant to the search warrant on the ground that the warrant was not valid. However, he has failed to include the warrant in the record. As we stated in State v. Haltom, 19 N.C. *478App. 646, 199 S.E. 2d 708 (1978), we cannot review the trial court’s conclusion that the warrant was valid where the warrant and supporting affidavit are not in the record on appeal.
[4] There is no merit to defendant’s contention that Officer Nobles’ opinion that the vegetable material seized was marijuana is incompetent. Officer Nobles testified that he had attended schools on the identification of marijuana, and that he had performed a field test on the substance. Even if this were not enough to qualify the officer’s expert testimony, defendant has waived his exception, for he made no motion to strike the testimony.
[5] Likewise, without merit is defendant’s assignment of error to the court’s finding that defendant was fully advised of his rights and knowingly and intelligently waived them. Defendant specifically contends that the evidence is not sufficient inasmuch as the finding is not supported by competent evidence that defendant’s rights were read to him from a card. Defendant offers no authority for his position that a defendant’s rights must be read from a card in the presence of witnesses, and we hold that there is no such requirement. The evidence on voir dire was uncontradicted to the effect that there was a voluntary, understanding statement. The court’s findings are conclusive since they are supported by competent evidence. State v. Fox, 277 N.C. 1, 175 S.E. 2d 561 (1970).
There is no merit to the contention that defendant’s motion for nonsuit was improperly denied. The test for sufficiency of the evidence in a criminal prosecution is well established, and we hold that the State has presented ample evidence to go to the jury.
No error.
Judges Campbell and Vaughn concur.