There are two issues presented on this review. First, is intent or negligence an element of the crime of mistreating animals, sec. 948.02,1 Stats. 1975. Second, was sufficient evidence presented to convict defendant-appellant Carl A. Stanfield, (Stanfield) of being party to the crime of mistreating animals, set forth in secs. 939.052 and 948.02, Stats. 1975. We hold that sec. 948.02 does not require proof of intent or negligence and that there is sufficient evidence in the record to sustain the jury verdict convicting Stanfield. We therefore reverse the decision of the court of appeals and reinstate the judgment of the trial court.
In November, 1976, Stanfield was charged with seven counts of being a party to the crime of mistreating animals. Following an eleven-day jury trial in Milwaukee county court, he was found guilty on three counts and not guilty on the other four. The following evidence was presented at that trial.
*556Stanfield testified as follows: He was the owner and operator of Canine College. He has used that tradename since the early 1960’s operating as a sole trader until 1976, when he incorporated the dog-training business as Canine College, Ltd., of which he was the principal owner. He conducted dog obedience classes and trained individual dogs at the homes of their owners. He also contracted with persons to individually train dogs away from the owner’s home. He would arrange to have the dogs picked up and delivered to persons with whom he had made contractual arrangements to train the dogs.
Stanfield further testified that one of the places with which he had contracted to train dogs was Pleasant Run Farms, near Fond du Lac, a kennel operated by Don Woods and Debbie Ullman. Stanfield provided food and supplies to Pleasant Run Farms and would send dogs to be trained. Woods and Ullman would train the dogs and were given the right to use the name Canine College. Stanfield would also help Woods and Ullman sell dogs which they had.
Stanfield testified that he used a method of training which involved a spiked collar and a short piece of chain which the handler rattled or threw at the dog to get its attention. He also used a stick with a piece of chain attached which he would throw at the dog if it were not responding properly. Persons with whom he contracted to train dogs under the auspices of Canine College also used this method. Other persons testified that, when training their dogs, Stanfield would strike the dogs with the stick and advised others to do so. There was also testimony that Stanfield possessed and advocated the use of an electric cattle prod to shock dogs if the above methods did not work.
The three counts which Stanfield was convicted of involved mistreatment of dogs belonging to Karen Nim-mer, Marie Van Wormer and William Towne. It was stipu*557lated that the Towne and Nimmer dogs were picked up from and returned to their owners by agents of Canine College pursuant to a contract between the owner and Canine College. Testimony established that this was also true concerning the Van Wormer dog. None of the owners were told where their dogs would be trained.
Ms. Nimmer testified that her dog, a Doberman Pinscher puppy, was in good shape, was housebroken, and had a pleasant disposition when she contacted Canine College. At that time it was gaining an average of four pounds a week. She talked to Stanfield twice while her dog was being trained and Stanfield informed her that the dog was doing fine but was not eating properly. When the dog was returned, it was thin, had pimples all over its body, was limping, the hair around its nose had worn off, it had diarrhea and acted dejected and frightened. The dog had gained no weight during its stay at Canine College and was no longer housebroken. She took the dog to the veterinarian several times within a short period of time following its return from Canine College to treat the maladies from which her dog was suffering when it was returned to her. She also stopped payment on her check to Stan-field and called him to express her shock at the condition of her dog.
Ms. Van Wormer testified that her dog, a Great Dane puppy, was friendly, docile, and got along well with small animals and children. She contacted Canine College and arranged to have the dog trained. While her dog was at Canine College, she spoke with Stanfield on the phone five times. Stanfield told her that the dog did not adapt well to male trainers, had not been eating right and had rubbed fur off of its back since it was too large to get through the door of the kennel run. When Stanfield returned the dog, he would not let Ms. Van Wormer see her dog until she had paid him. The *558dog had lost thirty pounds, had a large lump behind its ear and raw spots on its back, legs and tail arid acted frightened and confused. The dog never regained its former personality and became mean and irritable, prompting Ms. Van Wormer to give him away shortly thereafter.
Mr. Towne testified that his dog, a Doberman, was healthy, playful and friendly with children. He contacted Stanfield to have the dog trained. He spoke with Stanfield once or twice while the dog was away being trained and Stanfield assured him that the dog was doing well. When the dog was returned, after four weeks training, it had scratches on the inside of its legs, scabs inside of its ears, its feet were bleeding and it was excreting a malodorous sticky substance from its mouth. Because of this excretion, and the dog’s overall listlessness after it returned, Mr. Towne took the dog to a veterinarian and it eventually regained its health.
Upon his conviction, Stanfield was placed on two years probation with the first thirty days to be served in the county jail. He was ordered to pay a $600 fine, make full restitution to the three owners whose dogs he was convicted of mistreating, pay all the costs of the action, and perform seventy-five hours of community service work.3
Stanfield appealed his conviction to the Milwaukee county circuit court, which upheld the trial court verdict and sentence. He then appealed to the court of appeals which reversed the conviction and remanded the case to the trial court with orders to dismiss the complaint. The court of appeals held sec. 948.02, Stats., to require proof of intentional or negligent cruelty to ani*559mals, and found insufficient evidence to sustain the state’s burden of proof. The court of appeals noted that the evidence was sufficient to convict under the current statute,4 stating:
“Although the evidence would clearly justify a strict liability finding sufficient to impose a forfeiture under the present law, at the time the occurrences involved in this case the penalty imposed brought the crime within the definition of a misdemeanor and required proof of scienter.”
This court granted the state’s petition to review the court of appeals decision, and because we construe sec. 948.02, Stats. 1975, as not requiring proof of intent or negligence, we reverse.
Our first concern is determining the elements necessary to a conviction of being party to the crime of mistreating animals. Cruelty to animals is a particularly despicable offense because of the relative helplessness of animals when faced with inhumane humans willing or even anxious to mistreat them.
Pursuant to sec. 939.05, Stats., a person may be convicted of a crime if he directly commits it or intentionally aids and abets its commission. Section 948.02, Stats. 1975, makes it illegal for a person to “treat any animal, whether belonging to himself or another, in a cruel manner.” “Cruel” is defined by sec. 948.02, Stats. 1975, as “causing unnecessary and excessive pain or suffering or unjustifiable injury or death.”5
*560The court of appeals held that negligence or criminal intent is an element of sec. 948.02, Stats. It based this conclusion on State v. Collova, 79 Wis. 2d 473, 255 N.W.2d 581 (1977), wherein this court interpreted the crime of driving after one’s drivers license was revoked as requiring proof of intent despite the fact that the applicable statute did not mention criminal intent. However, Collova is not applicable to this case.
Collova interpreted a provision of the vehicle code. The crime of mistreating animals is part of the criminal code. Section 939.23, Stats. 1975, contains guidelines as to whether criminal intent is an element of an offense set forth in the criminal code.
“939.23 Criminal intent. (1) When criminal intent is an element of a crime in the criminal code, such intent is indicated by the term ‘intentionally,’ the phrase, ‘with intent to,’ the phrase ‘with intent that,’ or some form of the verbs ‘know’ or ‘believe.’ ”
In Collova, this court recognized the validity of sec. 939.23, but held it inapplicable to that case because the statute at issue was part of the vehicle, rather than the criminal code.6
Section 948.02, Stats., contains none of the words which sec. 939.23 sets forth as indicative of the element of intent. The predecessor to sec. 948.02, sec. 947.10(1) (a), Stats. 1971, explicitly required proof of intent.7
Section 948.02 was created by ch. 314, sec. 6, Laws of 1973. Senate Bill 16 which became ch. 314, contained *561the following Legislative Council note pertaining to sec. 948.02:8
“Note: This general anticruelty statute is a restatement of present s. 947.10(1) (a); however, the intent of the wrongdoer is no longer a controlling factor. Specific exception is provided for bona fide experiments and accepted veterinary practices.”
The comments of legislative advisory committees are relevant to the construction of a statute. Champlin v. State, 84 Wis. 2d 621, 625, 267 N.W.2d 295 (1978).
From the foregoing, we conclude that the legislature did not intend to require intent or negligence as an element of the crime of mistreating animals set forth in sec. 948.02, Stats.9 Nor does the fact that conviction under sec. 948.02 carries a potential prison sentence require that we read those elements into the offense.10
Because Stanfield was convicted of being a party to the crime of mistreating animals, there must be sufficient evidence presented to fulfill the requirements of *562sec. 939.05, Stats., that he either directly mistreated or aided and abetted another in mistreating animals. The jury was instructed, in accordance with Wis JI — Criminal No. 400, that Stanfield could be convicted of being a party to the crime of mistreating animals if he directly mistreated the animals, or if he intentionally aided and abetted such mistreatment. The jury was not required to state whether the conviction was for direct commission of the crime or intentionally aiding and abetting. In State v. May, 97 Wis. 2d 175, 189-192, 293 N.W.2d 478 (1980), this court specifically held that the party to a crime instruction which permitted the jury to choose among alternative ways by which a defendant could be a party to a crime was permissible.
In State v. Ehlenfeldt, 94 Wis. 2d 347, 359, 288 N.W.2d 786 (1980), this court stated the standard of proof which must be met to satisfy the “intentionally aids and abets” language of sec. 939.05:
“. . . [A] lthough intent does not appear to be an element of the substantive offense involved here, it is an element of the specific crimes with which Ehlenfeldt has been charged by virtue of sec. 939.05, Stats., the general party to a crime statute. Ehlenfeldt was charged and convicted of intentionally aiding and abetting Dan’s Country Boy Market in the violation of sec. 95.28(1). In Hawpetoss v. State, 52 Wis. 2d 71, 78, 187 N.W.2d 823 (1971), we stated:
“ ‘The elements of complicity, or aiding and abetting are that a person (1) undertakes conduct (either verbal or overt action) which as a matter of objective fact aids another person in the execution of a crime, and further (2) he consciously desires or intends that his conduct will yield such assistance.’
“It clearly follows from the above that Ehlenfeldt’s conviction can only be sustained if he was shown to have intentionally undertaken conduct which as a matter of objective fact aided Dan’s Country Boy Market in violating sec. 95.28(1), Stats.”
*563See also, Robinson v. State, 100 Wis. 2d 152, 167, 301 N.W.2d 429 (1981).
Whether a defendant possesses a particular intent is to be determined by the jury upon consideration of “the totality of the circumstances.” While the defendant’s testimony is relevant to this determination, his credibility and trustworthiness are for the jury to determine. Clark v. State, 92 Wis. 2d 617, 635, 286 N.W.2d 344 (1979). Direct testimony as to a defendant’s subjective intent is not necessary, as this court stated in Ehlen-feldt, supra:
“Although intent is usually not susceptible of direct proof, it may often be inferred from a person’s voluntary acts because of the almost self-evident principle of human conduct that people normally intend the natural and probable consequences of their acts.” Ehlenfeldt, supra, 94 Wis. 2d at 361.
We, therefore, hold that in order to sustain a conviction of intentionally aiding and abetting the crime of mistreating animals, there must be evidence presented sufficient to prove beyond a reasonable doubt that Stan-field knew that animals were being mistreated and engaged in conduct, the natural and probable consequence of which, as a matter of objective fact, aided another in such mistreatment.
In reviewing the record to determine whether sufficient evidence was presented to warrant a conviction, we apply the following standard of review, as set forth in State v. Burkman, 96 Wis. 2d 630, 643, 292 N.W.2d 641 (1980):
“When the defendant challenges the sufficiency of the evidence, the test is whether the evidence adduced, believed and rationally considered by the jury was sufficient to prove the defendant’s guilt beyond a reasonable *564doubt. The test is not whether this court is convinced of the defendant’s guilt beyond a reasonable doubt, but whether this court can conclude that the trier of fact could, acting reasonably, be convinced to the required degree of certitude by the evidence which it had a right to believe and accept as true. Reversal is only required when the evidence considered most favorably to the state and the conviction is so insufficient in probative value and force that it can be said as a matter of law that no trier of facts acting reasonably could be convinced to that degree of certitude which the law defines as ‘beyond a reasonable doubt.’ ” (citations omitted).
A conviction may be based upon circumstantial evidence, however when circumstantial evidence is relied upon, as here, a conviction should be upheld if the evidence is strong enough to exclude to a moral certainty every reasonable hypothesis of innocence. Frankovis v. State, 94 Wis. 2d 141, 148, 287 N.W.2d 791 (1980).
After reviewing the record, we conclude that the evidence presented, construed most favorably to the state, was sufficient to convince a reasonable trier of fact beyond a reasonable doubt that Stanfield had been a party to the crime of mistreating animals.
The persons who trained the dogs had been instructed how to do so by Stanfield. The methods and devices advocated and used by Stanfield can easily cross over the line and become the means of animal abuse as the jury had the right to conclude from the physical condition of the dogs at the time they were returned to their owners. The owners of the dogs that Stanfield was convicted of mistreating spoke with Stanfield on the phone while the dogs were being trained. In those conversations, Stanfield described the dogs’ condition and how the training was proceeding. Stanfield personally returned Ms. Van Wormer’s dog to her. Stanfield was the person with whom all of the owners contracted to have their dogs trained, and Stanfield arranged with them for the dogs to be picked up and returned.
*565The condition of the dogs when they were returned after training would support a jury finding that they had been mistreated while being trained. The evidence of the telephone calls by the dog’s owners to Stanfield, in which Stanfield gave them information evidencing an awareness of the dog’s condition and training could convince a reasonable jury that Stanfield knew how the dogs were being treated during their training and, a fortiori, knew that they were being mistreated. The evidence that Stanfield arranged to pick up the dogs and return them to their owners, coupled with Stanfield’s presence when Ms. Van Wormer’s dog was returned to her and his conversations with Ms. Nimmer in which she expressed her distress over her dog’s condition upon its return, would support a finding that he took actions which, as a matter of objective fact, aided others in mistreating animals and consciously intended to provide such assistance.
We conclude that the above evidence, when viewed most favorably to the state, was sufficient to convince a reasonable jury beyond a reasonable doubt that Carl Stanfield was guilty of being a party to the crime of mistreating animals.
By the Court. — The decision of the Court of Appeals is reversed and the judgment of the trial court is reinstated.
“948.02 Mistreating animals. No person may treat any animal, whether belonging to himself or another, in a cruel manner. This section does not prohibit bona fide experiments carried on for scientific research or normal and accepted veterinary practices.”
“939.05. Parties to crime. (1) Whoever is concerned in the commission of a crime is a principal and may be charged with and convicted of the commission of the crime although he did not directly commit it and although the person who directly committed it has not been convicted or has been convicted of some other degree of the crime or of some other crime based on the same act.
“(2) A person is concerned in the commission of the crime if he:
“(a) Directly commits the crime; or
“(b) Intentionally aids and abets the commission of it; . . .”
Stanfield was sentenced under sec. 948.18, Stats. 1975, which reads:
“948.18 Penalties. (1) Any person violating s. 948.02, 948.03, 948.05, 948.06, 948.07, 948.08, 948.09, 948.13, 948.14 or 948.15(1) may be fined not more than $500 or imprisoned not more than one year in the county jail or both.”
Subsequent to the commencement of this action, the penalties for a conviction under the crimes against animals statutes were revised. Under the current law, a person convicted under sec. 948.02, Stats., which remains unchanged, is subject to a $200. forfeiture unless it was found that he did so negligently or with intent, in which case he was subject to a nine month prison sentence and a $10,000. fine. See, sees. 948.18(1), 939.51 and 939.52, Stats. 1979-80.
“948.01 Definitions. In this chapter: . . .
“(2) ‘Cruel’ means causing unnecessary and excessive pain or suffering or unjustifiable injury or death.”
Collova, supra, 79 Wis. 2d at 480, n. 2.
“947.10 Cruelty to animals. (1) Whoever does any of the following may be fined not more than $500 or imprisoned not more than one year in county jail or both: . . .”
“(a) Intentionally tortures any animal, or without justification kills any domestic animal of another without the owner’s consent; . . . (emphasis added).
This note is also appended to see. 948.02, Stats. 1979-80.
The indicia of a legislative intent to remove criminal intent as an element of sec. 948.02, Stats., distinguishes this case from State v. Alfonsi, 33 Wis. 2d 469, 147 N.W.2d 660 (1967), in which this court was persuaded by legislative history, including the text of successive statutes on the same subject and committee reports, that criminal intent was an element of the crime of bribery of a public officer as defined by sec. 946.10(2), Stats. 1965. Alfonsi, supra, 33 Wis. 2d at 475-476. While legislative history persuaded this court to hold that intent must be proved in Alfonsi, those same aids to construction require that we not read an element of intent into sec. 948.02.
This court has upheld strict liability statutes containing far more severe penalties than that at issue here. See, Redepenning v. State, 60 Wis. 2d 471, 480-481, 210 N.W.2d 673 (1973) (rape: 30 year maximum prison sentence); Flowers v. State, 43 Wis. 2d 352, 359-360, 168 N.W.2d 843 (1969) (indecent behavior with a child: 10 year maximum prison sentence).