OPINION
I. Introduction
In this appeal, Appellant Darrell Jay Keehn raises a single point challenging the trial court’s denial of his motion to suppress. Keehn contends that officers’ war-rantless entry into an unoccupied van that was parked in the driveway in front of his residence violated the Fourth Amendment and Article I, Section 9 of the Texas Constitution. Because in this case a police officer observed a propane tank that had a bluish-green discoloration near its valve in plain view in the back of a van as he *55 walked down the driveway and by the van on his way to the front door of the residence to conduct a “knock and talk” and because the officer immediately believed the propane tank was associated with the criminal activity, the plain view doctrine applies. Accordingly, we will affirm the trial court’s denial of Keehn’s motion to suppress.
II. Factual and Procedural History
A theft occurred in a residential area in Wichita County. An eyewitness to the theft told investigators with the Wichita County Sheriffs Department that she saw the suspected thieves flee to the back door of 1811 Cameron Lane — Keehn’s home— and later leave that residence in a van. A few days later, Deputy Monty Deford drove to Keehn’s residence to conduct a follow-up interview with the residents of that house concerning the theft. Deputy Deford observed the previously described van parked in the driveway in front of the house and called the lead investigator, Sergeant Randy Elliott, to meet him at Keehn’s house. As Deputy Deford walked up the driveway toward the residence’s front door, he walked by the van and peered inside it; he observed a propane bottle lying in the back of the van and bluish-green discoloration or corrosion was visible around the neck of the bottle. Deputy Deford believed the discoloration or corrosion around the neck of the bottle or tank to be an indication that the bottle or tank contained anhydrous ammonia, used in the manufacture of methamphetamine. Deputy Deford called the drug task force to investigate the possible anhydrous ammonia in the van.
Wichita Falls Police Officer John Spra-gins, a member of the North Texas Drug Task Force, responded to Deputy Deford’s call to Keehn’s home. Officer Spragins saw the van parked in the driveway, looked inside the van, observed the propane tank — the type used for an outdoor gas grill — and observed the discoloration on the tank’s valve. He believed that the discoloration indicated that the propane tank had been used to store anhydrous ammonia; he knew that a gas grill propane tank is not an approved container to carry anhydrous ammonia and that anhydrous ammonia is utilized in the manufacture of methamphetamine.
Officer Spragins seized the tank, tested the substance in the tank, and determined that it was anhydrous ammonia. Because the propane tank was not an authorized container for transporting anhydrous ammonia, Officer Spragins arrested Keehn. The grand jury indicted Keehn for possession of anhydrous ammonia with intent to unlawfully manufacture a controlled substance, namely, methamphetamine.
Keehn filed a motion to suppress the evidence seized from the van. After a hearing, the trial court denied Keehn’s motion, and Keehn subsequently entered into a plea bargain agreement. He pleaded guilty in exchange for an agreement that the prosecution would recommend seven years’ confinement in the Texas Department of Criminal Justice Institutional Division and that the trial court would certify his right to appeal the suppression ruling. This appeal followed.
III. Legal Search and Seizure
In his sole point, Keehn argues that the search of the van and the seizure of the tank and its contents violated the Fourth Amendment of the United States Constitution and Article I, Section 9 of the Texas Constitution. Specifically, Keehn alleges that the plain view exception to the warrant requirement does not apply here because it was not immediately apparent to officers that the propane tank contained anhydrous ammonia and because the offi *56 cers did not have a lawful right to enter the driveway or the van.
A.Standard of Review
We review a trial court’s ruling on a motion to suppress evidence under a bifurcated standard of review.
Carmouche v. State,
Stated another way, when reviewing the trial court’s ruling on a motion to suppress, we must view the evidence in the light most favorable to the trial court’s ruling.
State v. Kelly,
B. Findings and Conclusions
After the suppression hearing, the trial court made the following findings and conclusions:
1. The defendant had standing to complain about the search of the van parked by his house.
2. The propane tank found in the referenced van was in plain view to officers has [sic] they made their way to the front door of the defendant’s house on the normal course used to reach the front door.
3. The peace officers had the right to be in the place they were to see the propane tank.
4. The propane tank had a discoloration consistent with tanks that contained anhydrous ammonia.
5. The propane tank was not designed to contain anhydrous ammonia.
6. The peace officers had probable cause to believe that a crime was being committed and therefore had the right to seize the propane tank from the van.
C. Warrantless Searches and Seizures
The Fourth Amendment protects against unreasonable searches and seizures. U.S. Const, amend. IV. To suppress evidence based on an alleged Fourth Amendment violation, the defendant bears the initial burden of producing evidence to rebut a presumption of proper police conduct.
Torres v. State,
Whether a search is reasonable is a question of law that we review de novo.
Kothe v. State,
One of those specifically defined and well-established exceptions is the “plain view” doctrine. Although commonly classified as an exception to the warrant requirement, the plain view doctrine is not truly an “exception” to the warrant requirement because the seizure of property in plain view involves no invasion of privacy and is presumptively reasonable.
Walter v. State,
D. Analysis
At the suppression hearing, Keehn satisfied his burden of proving that the search occurred without a warrant. The burden then shifted to the State to prove that the search and seizure were reasonable.
See Torres,
1. Lawful Vantage Point
To meet its burden, the State was first required to prove that the officers had a right to be where they were at the time they observed the propane tank.
Walter,
It is certainly true that the Fourth Amendment protections extend to the cur-tilage of a home.
See Oliver v. United States,
The evidence is undisputed that Deputy Deford initially observed the propane tank inside the van while walking to the front door to conduct a follow-up interview with Keehn. In Duhig, law enforcement officers walked to the defendant’s front door, knocked, peered inside his front door window, and observed marijuana, a scale, and a bong on a table in the living room. Id. at 633. The court of appeals held that the law enforcement officers were free to observe evidence in plain view while rightfully at the front door. Id. at 636. Specifically, the court held that “[w]hat a person knowingly exposes to the public, even in his own home, is not a search subject to Fourth Amendment protection.” Id.
We hold that the evidence supports the trial court’s findings of fact and that the correct application of the law to those facts support the trial court’s determination that law enforcement officers had a right to be where they were when they observed the propane tank.
See Walter,
2. Probable Cause to Believe Propane Tank Was Evidence of Crime
The second prong of the plain view doctrine requires the State to prove that it was immediately apparent that the propane tank constituted evidence. See id. Put another way, the State had to prove that law enforcement officers had probable cause to associate the propane tank with criminal activity. See id.
The criminal activity suspected by Deputy Deford and Officer Spragins was that for which Keehn was indicted — possessing anhydrous ammonia with intent to unlawfully manufacture a controlled substance, namely, methamphetamine. Officer Spra-gins also testified that the propane tank was not “an approved container to carry ammonia.”
Keehn correctly argues that possession of anhydrous ammonia is not illegal per se, but it is illegal to possess or transport it with the intent to manufacture a controlled substance. Tex. Health & Safety Code Ann. § 481.124(a)(1) (Vernon 2005). And the intent to manufacture a controlled substance is presumed when anhydrous ammonia is stored or transported in a container or receptacle not designed and manufactured to lawfully hold or transport anhydrous ammonia, like the propane tank at issue in this case.
See
Tex. Health
&
Safety Code Ann. § 481.124(b)(1) (Vernon 2005). Thus, the officers here possessed probable cause to believe that the propane tank was associated with criminal activity.
See Arrick v. State,
Keehn relies on
Pollock v. State,
Second, in Pollock the appellate court held that the record did not demonstrate that the sheriff was qualified as an expert to testify about applicable standards or regulations governing containers for anhydrous ammonia. Id. at 790. But here, Officer Spragins testified at the suppression hearing that he had been assigned to the North Texas Drug Task Force for five years, had traveled to Quantico, Virginia to attend basic and advanced training conducted by the D.E.A. concerning clandestine methamphetamine labs, and had investigated the manufacture and production of methamphetamine in North Texas many times. Officer Spragins testified that the valve on the propane tank had a bluish-green discoloration, which in his opinion “indicated that it had been used to store anhydrous ammonia,” which was used to manufacture methamphetamine. Officer Spragins also performed a “drager pump” test on the propane tank, which revealed positive results for anhydrous ammonia. Officer Spragins also testified that the propane tank was not an approved container to carry ammonia. And, the intent to manufacture a controlled substance is presumed when anhydrous ammonia is stored in a container not designed and manufactured to hold it, like the propane tank here. Tex. Health & Safety Code Afín. § 481.124(b)(1).
Viewing the evidence in the light most favorable to the trial court’s ruling, we hold that law enforcement officers had probable cause to believe that the propane tank — located inside the van that was parked in the driveway in front of Keehn’s home — was associated with criminal activity.
See Kelly,
IV. Conclusion
Having overruled Keehn’s sole point on appeal, we affirm the trial court’s ruling denying Keehn’s motion to suppress.
