JUSTICE COOK delivered the opinion of the court:

I. BACKGROUND

On March 30, 2001, Macon County State's Attorney ScottA. Rueter charged defendant by information with two counts ofunlawful possession of a methamphetamine-manufacturing chemicalwith intent to manufacture methamphetamine. Count I alleged thatdefendant possessed pseudoephedrine with the intent to manufacture 30 to 150 grams of a substance containing methamphetamine, aClass X felony carrying a sentencing range of 6 to 30 years'imprisonment. 720 ILCS 570/401(a)(6.6)(A) (West Supp. 2001). Count II alleged that defendant possessed pseudoephedrine withthe intent to manufacture less than 15 grams, a Class 2 felony. 720 ILCS 570/401(d-5) (West Supp. 2001).

Defendant's jury trial was held on February 24 and 25,2003. James Cottrell, a loss-prevention officer at a Wal-Mart inDecatur, testified that on March 1, 2001, he notified law enforcement that he saw defendant, accompanied by Tammy Garland,purchase three boxes of cold pills, leave the store, and get intoa brown van. Sometime later, defendant exited the van, put aWal-Mart bag in the garbage can in the front of the store, andwent back into the store. Cottrell instructed store employees tocollect the garbage bag and take it to his office. Todd Kilby ofthe Illinois State Police recovered empty boxes and blister packsof cold pills, as well as the receipt for the purchase, from aWal-Mart bag in the garbage. Defendant left the store for thesecond time carrying a large plastic tote.

Decatur police officer Richard Hughes testified that hehad been called to do surveillance of defendant and Garland andsaw them leave the Wal-Mart parking lot in a brown van. Law-enforcement officers observed Garland drive the van to the Mt.Zion Plaza Wal-Mart. Decatur police officer Carl Carpentertestified that he saw defendant go into the store and come backout carrying a can of Coleman fuel and another Wal-Mart bag. Garland then drove defendant to a Dollar General, where Hughesand Carpenter saw defendant go into the store and come back outcarrying some bulky Dollar General bags.

After defendant and Garland left the Dollar Generalparking lot, Decatur police officers pulled the van over for atraffic violation. Carpenter arrived, spoke with defendant, andconducted a consensual search of defendant's person. Carpentertestified that he felt something inside defendant's pants. JamesRoot of the Illinois State Police found in defendant's crotcharea a pseudoephedrine box containing several blister packs ofpseudoephedrine pills and many loose pseudoephedrine pills. Officers recovered 552 pseudoephedrine pills in all. Carpenter searched the van and found 11 glass containers inside the DollarGeneral bags, a can of Coleman fuel, and a bag of ice melt.

Carpenter and Terry Eck of the State Police Task Forceboth testified that they interviewed defendant at the law-enforcement center. They stated that defendant told them that heand a friend, Billy Morrison, had decided to collect 5,000pseudoephedrine pills, 5 cans of Coleman fuel, and a couple ofpackages of lithium batteries to manufacture 100 grams of methamphetamine. Defendant said that he had gotten six to eightpackages of pseudoephedrine at one store and a couple of packagesat another and that the Coleman fuel and glass jars were to beused in the production of methamphetamine.

The trial court qualified Kilby as an expert after he outlined his training and experience in the areas of methamphetamine manufacture and distribution, including his involvement in500 methamphetamine investigations. Kilby testified that he hasactually "cooked" methamphetamine as part of his training usingthe lithium-ammonia method, the most commonly used method in thearea. He had seen up to a 90% yield rate, meaning 90% of thepseudoephedrine is converted to methamphetamine. Based on thatrate, he calculated that 552 pseudoephedrine pills could yield upto 14.994 grams of methamphetamine. Kilby also stated that astudy conducted by two people employed by the Iowa Division ofCriminal Investigation regarding yield rate is much disputedwithin the forensic field. Kilby believed that defendant possessed the 552 pseudoephedrine pills with the intent to manufacture methamphetamine.

Defendant offered the expert testimony of Terry Martinez, Ph.D., an associate professor of pharmacology and toxicologyat the St. Louis College of Pharmacy. He identified the 552pills offered into evidence by the State as 30-milligram tabletsof Equate pseudoephedrine. Martinez testified that with a 100%yield rate, which no chemist could achieve, the most someonecould produce from that amount of pseudoephedrine is 15.25 gramsof methamphetamine. Martinez stated that Iowa chemists hadtested a number of recipes and had gotten from 15% to 63% yieldrates and that the Iowa study was the best. Using the 63% rate,552 pseudoephedrine pills would yield 10.43 grams of methamphetamine.

The jury found defendant guilty of unlawful possessionof a methamphetamine-manufacturing chemical with the intent tomanufacture 30 to 150 grams of a substance containing methamphetamine. Defendant filed a posttrial motion, arguing in part thatthe evidence was insufficient to prove defendant's guilt beyond areasonable doubt because the State did not prove that defendantcould manufacture more than 30 grams of methamphetamine from the552 pseudoephedrine pills. The trial court denied defendant'smotion. This appeal followed.

II. ANALYSIS

Under the Illinois Controlled Substances Act (Act), itis "unlawful for any person knowingly to *** (ii) possess anymethamphetamine[-]manufacturing chemical listed in paragraph (z-1) of [s]ection 102 with the intent to manufacture methamphetamine or the salt of an optical isomer of methamphetamine or ananalog thereof." 720 ILCS 570/401 (West Supp. 2001). Section102 defines "methamphetamine[-]manufacturing chemical" toinclude pseudoephedrine. 720 ILCS 570/102(z-1) (West Supp.2001). The Act provides that a person who violates section 401is subject to a term of imprisonment of "not less than 6 yearsand not more than 30 years for the possession of anymethamphetamine[-]manufacturing chemical *** with intent tomanufacture 30 grams or more but less than 150 grams of anysubstance containing methamphetamine, or salt of any opticalisomer of methamphetamine, or an analog thereof." 720 ILCS570/401(a)(6.6)(A) (West Supp. 2001). A person who violatessection 401 where less than 15 grams of methamphetamine isinvolved is guilty of a Class 2 felony, for which a sentence ofnot less than 3 years and not more than 7 years is possible. 720ILCS 570/401(d-5) (West Supp. 2001); 730 ILCS 5/5-8-1(a)(5) (WestSupp. 2001).

Defendant first argues that the State did not prove anelement of the charged offense beyond a reasonable doubt. Defendant correctly states that the prosecution had to provebeyond a reasonable doubt that he intended to manufacture 30 to150 grams of methamphetamine, but no one could produce 30 to 150grams of methamphetamine from the amount of pseudoephedrine pillsfound on his person.

We review a challenge to the sufficiency of the evidence to determine whether, after viewing the evidence in thelight most favorable to the prosecution, any rational trier offact could have found the essential elements of the crime beyonda reasonable doubt. People v. Collins, 214 Ill. 2d 206, 217, 824N.E.2d 262, 267 (2005). We will not reverse a conviction unlessthe evidence is so improbable, unsatisfactory, or inconclusivethat it creates a reasonable doubt of defendant's guilt. Collins, 214 Ill. 2d at 217, 824 N.E.2d at 267-68. If a courtdetermines that the evidence is insufficient to establish thedefendant's guilt beyond a reasonable doubt, the defendant'sconviction must be reversed. People v. Woods, 214 Ill. 2d 455,470, 828 N.E.2d 247, 257 (2005). There must be some evidencegiving rise to a reasonable inference of the defendant's guilt;the State may not leave to conjecture or assumption essentialelements of the crime. People v. Laubscher, 183 Ill. 2d 330,335-36, 701 N.E.2d 489, 491 (1998).

The State concedes that defendant did not possessenough pseudoephedrine to manufacture 30 grams or more of methamphetamine; there is no question that defendant could not haveactually made 30 or more grams of methamphetamine from 552pseudoephedrine pills. However, it argues it only needed toprove that defendant possessed the pseudoephedrine with theintent to manufacture between 30 and 150 grams of a substancecontaining methamphetamine. The State relies on Carpenter's andEck's testimony that defendant told them that he and a friend haddecided to collect 5,000 pseudoephedrine pills to make 100 gramsof methamphetamine.

Other cases before this court have involved testimonyregarding the amount of methamphetamine that one could producefrom a given amount of pseudoephedrine pills actually possessedby particular defendants. The circumstances of this case areunique, however, in that the jury convicted defendant of intentto manufacture an amount of methamphetamine he could not havepossibly produced from the pseudoephedrine in his possession. Whether the State proved defendant's guilt beyond a reasonabledoubt depends, then, upon whether defendant's possession of 552pseudoephedrine pills and his statement that he wanted to make100 grams of methamphetamine are sufficient to establish that heintended to manufacture 30 to 150 grams.

It is not necessary that a person possessingmethamphetamine-manufacturing chemicals actually manufacture ordeliver methamphetamine before an offense is committed. It isonly necessary that the person possessing those chemicals do so"with the intent to manufacture methamphetamine." 720 ILCS570/401(ii) (West Supp. 2001). Intent to manufacture is clearlya substitute for actual manufacture or delivery. But how is theoffense classified, how is the penalty established, when there isno manufacture only an intent to manufacture? Intent is a ratherelastic concept. Every burglar would like to steal a milliondollars but most of them are unable to come close to that amount. If the key in this case is intent, could possession of onepseudoephedrine pill have supported a conviction of intent tomanufacture more than 30 grams of methamphetamine? If defendanthad been arrested before he purchased any materials, could therebe a conviction of intent to manufacture more than 30 grams? SeePeople v. Stanley, 146 Ill. App. 3d 912, 918-19, 497 N.E.2d 496,500 (1986) (there must be evidence to satisfy the court that aconfession was not the product of imagination).

Though no authority directly on point exists, the lawof attempt provides some guidance. Illinois courts differentiatebetween mere preparation and a substantial step toward committingan offense. See People v. Terrell, 99 Ill. 2d 427, 433, 459N.E.2d 1337, 1340 (1984); People v. Burleson, 50 Ill. App. 3d629, 632, 365 N.E.2d 1162, 1165 (1977). Determining whether anact constitutes a substantial step "can only be accomplished byevaluating the facts and circumstances of the particular case." Terrell, 99 Ill. 2d at 433, 459 N.E.2d at 1340. "The essentialquestion *** is whether, given the intent to commit a specificoffense, the defendant performed acts bringing him in '"'dangerous proximity to success'"' in carrying out his intent." Peoplev. Morissette, 225 Ill. App. 3d 1044, 1046, 589 N.E.2d 144, 146(1992), quoting Terrell, 99 Ill. 2d at 434, 459 N.E.2d at 1341,quoting People v. Paluch, 78 Ill. App. 2d 356, 360, 222 N.E.2d508, 510 (1966), quoting Hyde v. United States, 225 U.S. 347,388, 56 L. Ed. 1114, 1134, 32 S. Ct. 793, 810 (1912) (Holmes, J.,dissenting). For example, someone has taken a substantial stepwhen he or she "'possesses the materials necessary to carry outthe crime, at or near the place contemplated for its commission.'" Terrell, 99 Ill. 2d at 435, 459 N.E.2d at 1341, quotingPeople v. Reyes, 102 Ill. App. 3d 820, 835, 429 N.E.2d 1277, 1290(1981).

In this case, defendant only had 552 pseudoephedrinepills, less than half of the amount defendant would need toproduce even 30 grams of methamphetamine using the State'sgenerous 90% yield rate. (Notably, defendant's statement that heneeded 5,000 pills to make 100 grams of methamphetamine revealsthat he only expected a 66.3% yield rate.) He had one can ofColeman fuel, not the five cans that Carpenter and Eck testifieddefendant told them he needed. Further, though Kilby testifiedthat he believed defendant possessed the 552 pseudoephedrinepills with the intent to manufacture methamphetamine, he did notclaim to know that defendant intended to manufacture more than 15grams of methamphetamine.

Perhaps the alert Wal-Mart employee and the efforts oflaw enforcement prevented defendant from acquiring morepseudoephedrine and other necessary supplies to manufacture afull 100 grams of methamphetamine. But perhaps defendant wouldhave taken the 552 pseudoephedrine pills and made 14.994 grams orless before setting out to purchase more pseudoephedrine. Without evidence establishing a "substantial step," defendantcannot be punished for intent to manufacture a greater amount.

In response to the dissent, it is clear that a defendant can be convicted of unlawful possession of amethamphetamine-manufacturing chemical with intent to manufacturemethamphetamine if he is arrested at an early stage in hisendeavor. The question presented in this case is the classification of offenses: whether more evidence is required to convict adefendant of intent to manufacture 30 to 150 grams than isrequired to convict a defendant of intent to manufacture lessthan 15 grams, or whether we just leave the matter up to thejury.

Finally, defendant argues that his trial counsel wasineffective because he did not request a Frye hearing (see Fryev. United States, 293 F. 1013 (D.C. Cir. 1923)) on the method theState's expert used to calculate methamphetamine weight where nomethamphetamine was manufactured. This contention is withoutmerit. Defendant's own expert testified that the procedures toproduce methamphetamine "are very similar to other chemicalprocedures. There is nothing unique about them. This is simplechemistry." Additionally, the State and defense experts agreedthat defendant could not have manufactured 15 grams or more ofmethamphetamine from the 552 pseudoephedrine pills; they onlydisagreed over the appropriate yield rate.

We therefore direct the trial court to reduce theconviction for possession of pseudoephedrine with intent tomanufacture 30 to 150 grams of a substance containing methamphetamine to possession of pseudoephedrine with the intent to manufacture less than 15 grams of a substance containing methamphetamine.

III. CONCLUSION

For the reasons stated, we affirm as modified andremand this case with directions to reduce the conviction oncount II to possession of pseudoephedrine with intent to manufacture less than 15 grams of a substance containing methamphetamineand resentence defendant thereon.

Affirmed as modified and remanded with directions.

APPLETON, J., specially concurs.

STEIGMANN, J., dissents.

I concur with the decision of the majority but writeseparately to address one point addressed by its opinion. This issue has been previously addressed by this court in decisionsissued pursuant to Rule 23 (166 Ill. 2d R. 23) and not previouslypublished.

In prosecutions charging the possession of precursorsubstances with the intent to produce methamphetamine, thequestion will always arise of how much methamphetamine could beproduced from the recovered quantity of pseudoephedrine. Fromthe record in this case, as well as numerous others before thiscourt, it is abundantly clear that a formula exists for theconversion of precursor material into a quantity of methamphetamine. That formula is commonly accepted by the scientificcommunity and, in essence, is operable by the application ofmathematics. The only variables in the formula are the skill ofthe "cookers," the equipment used by them, and the location ofthe production.

It is these variables that produce the plethora ofdifferent conversion ratios of raw material to product--rangingfrom .92 to .40--seen by this court as well as other state andfederal courts throughout the country. The gravamen of theoffense, possession with the intent to manufacture a certainamount, should not depend on a variable either outside thecontrol of the defendant (as here, where defendant was only aprocurer of precursors for another) or within the control of theultimate manufacturer. The amount of end product should becharged and proved by the State based on a conversion formulabased on what is possible to be produced, i.e., the maximum,regardless of extraneous skill or environmental factors.

The conversion formula is what it is--the maximumamount that can be produced without regard of the argued ineptitude of the person who could be charged with transforming ahealthful product into poison. See People v. Redenbaugh, No. 4-03-0667 (June 23, 2005) (unpublished order under Supreme CourtRule 23).

Based upon this analysis, the oft-debated Iowa study ofthe potential yield of methamphetamine from the precursor drugpseudoephedrine is of no usefulness in the State of Illinois. Tohold otherwise would involve the courts of this state in aqualitative analysis of the experimental and environmentalvariables involved in the production of methamphetamine, anexercise that is both unnecessary and unwise.

Because I do not agree that this court should reducedefendant's conviction of possession of a methamphetamine-manufacturing chemical with the intent to manufacture 30 to 150 gramsof a substance containing methamphetamine to the lesser offenseof possession of a methamphetamine-manufacturing chemical withthe intent to manufacture less than 15 grams of a substancecontaining methamphetamine, I dissent. The crux of this offenseis defendant's intent, not his ability, to commit the crimecharged. The majority interprets section 401(a)(6.6)(A) toinclude an additional element--namely, that a defendant possessnot just the intent to manufacture 30 to 150 grams of methamphetamine, but that he also have the present ability to do so. Thus,the fact that defendant, at the time of his arrest, did notpossess enough of the necessary chemicals to manufacture 30 to150 grams of a substance containing methamphetamine simply doesnot matter.

Usually, the trier of fact is called upon to determinea defendant's intent from the circumstances surrounding hisconduct. However, in this case, the State presented directevidence regarding defendant's intent through the testimony ofpolice officers Carpenter and Eck. They testified that defendanttold them that he and a friend were going to gather the necessaryingredients to manufacture 100 grams of methamphetamine. Inlight of this testimony, I fail to see how this court can conclude that no reasonable juror, viewing this evidence in thelight most favorable to the State, could find that the State hadproved defendant guilty beyond a reasonable doubt of the specificintent as charged--that is, to manufacture 30 to 150 grams of asubstance containing methamphetamine.

In this time of concern about terrorism, it is easy toimagine a case in which a defendant is charged with possession ofexplosive equipment with the intent to blow up a building andkill people. (For purposes of this hypothetical, it does notreally matter if the charge would be attempted murder or someother offense in the criminal code that would best fit thesefacts.) Assume in this hypothetical that, at the time of hisarrest, the defendant was in possession of some bomb-makingequipment but, at that specific moment in time, he did not haveall he needed for a working bomb because he had not yet acquiredblasting caps. Assume further that he told two police officersthat the reason he had this equipment was because he intended tomake a bomb to blow up a governmental facility and kill thepeople inside. Under these circumstances, I do not believe anycourt would set aside his conviction merely because at the timeof his arrest the defendant did not possess all he needed to makea working bomb.

I believe this scenario applies to the case before us. Defendant had some of the makings for methamphetamine but, at thetime of his arrest, did not yet possess all he needed to make asmuch methamphetamine as it was clearly his intent to make. Ifthe jury believed the testimony of the officers (as it wasentitled to) that defendant intended to manufacture 100 grams ofmethamphetamine, then the only conclusion to be drawn from thecircumstances of this case is that the police arrested him beforehe was able to obtain all the chemicals needed to meet his goal. This good police work does not reduce defendant's culpability--orcriminal liability--for the crime he was charged with and intended to commit.