OPINION
NYE, Chief Justice.Appeal is taken from a judgment of conviction for possessing between 200 and 2000 pounds of marihuana. Punishment was assessed at twelve years. Appellant Jose Francisco Leal complains, in three points of error, that the evidence of his guilt should have been suppressed due to an illegal search. A fourth point of error urges that reversal is required due to an improper stipulation of evidence.
Both the hearing on motion to suppress and the trial on the merits were before the trial court. Appellant reurged his suppres*905sion motion at trial. The principal witness at both the suppression hearing and the trial was Officer Victor Escalón, an agent of the Texas Department of Public Safety. His testimony at the suppression hearing is summarized as follows. Escalón received a tip from a confidential informant, who had given reliable information “about two” times in the past, that a shipment of marihuana had come across from Mexico. The next day, February 1, 1985, the informant told Escalón that the marihuana had been taken to a ranch of approximately fifteen acres in Hidalgo County. The informant particularly described a location north of the town of Mercedes and told Escalón that two trailers, one a white mobile home trailer and one a colored trailer from a tractor-trailer rig, would be surrounded by an old, beat-up fence. Escalón located the described ranch and set up surveillance to the north of it that same day. He saw several vehicles enter the ranch by a gate, and one vehicle left. Then a bright orange Pontiac Trans Am arrived and backed up to the tractor trailer. Someone removed some things from the Trans Am’s trunk and put them in the back seat, then some packages were taken from the tractor trailer and placed in the trunk of the Trans Am. The packages taken from the tractor trailer were wrapped similarly to marihuana that Escalón had seen in his prior experience.
Escalón followed the Trans Am when it left, and the vehicle immediately met a pickup truck that was parked on the highway. The Trans Am’s driver exchanged places with two men in the pickup and drove the pickup away. Escalón stopped the Trans Am after about a mile. He noticed that the spare tire was in the back seat, and that a strong odor of marihuana emanated from the car. The driver consented to a search of the trunk, which revealed a large amount of marihuana.
Escalón arrested the two occupants of the Trans Am and called for assistance from other law enforcement officers. When help arrived, he and about four other officers returned to the ranch. The gate was locked, and a “Keep Out” sign had been posted. Escalón took bolt cutters, severed the chain which locked the gate, and the officers entered the ranch. The two trailers, as well as a permanent building, sat about in the middle of the ranch. Appellant was the only person on the premises. Escalón approached appellant, who described himself as the caretaker of the premises. He consented to a search of the premises, signing a consent-to-search form and producing the keys to the tractor trailer from the right pocket of the coat he was wearing. Escalón found, according to his estimate, approximately 650 pounds of marihuana in the tractor trailer.
Appellant testified at the trial on the merits for the limited purpose of establishing his “standing” to contest the legality of the search. He testified that the lessor of the ranch had given appellant permission to reside there in return for performing some caretaking duties. Appellant had been given authority to order trespassers off the ranch. He also was charged with mending the fence and looking after the cattle.
Appellant initially contends that the warrantless search of the ranch was illegal under the United States and Texas Constitutions, because the law enforcement officers entered without first securing a warrant. Recently, in United States v. Dunn, — U.S. -, 107 S.Ct. 1134, 94 L.Ed.2d 326 (1987), the United States Supreme Court reaffirmed the “open fields” doctrine by holding that no violation of the fourth amendment occurred when law enforcement officers crossed several fences on the defendant’s property to obtain a view of suspected illegal activity. The Court in Dunn followed the rule begun by Hester v. United States, 265 U.S. 57, 58, 44 S.Ct. 445, 446, 68 L.Ed. 898 (1924), and expanded by Oliver v. United States, 466 U.S. 170, 104 S.Ct. 1735, 80 L.Ed.2d 214 (1984), that “there is no constitutional difference between police observations conducted while in a public place and while standing in the open fields.” Dunn, — U.S. at-, 107 S.Ct. at 1141. Neither is the technical tres*906pass of the officers in the case before us constitutionally significant. A trespass at common law is not the equivalent of a “search” in the constitutional sense. Oliver, 446 U.S. at 183, 104 S.Ct. at 1743. A warrant was therefore unnecessary as a prerequisite to the officers’ entry on the ranch.
Appellant nevertheless contends that the “open fields” doctrine has been abandoned under Texas constitutional analysis in favor of a “legitimate expectation of privacy” test. However, appellant supports his argument only by citing Goehring v. State, 627 S.W.2d 159 (Tex.Crim.App.1982). Goehring, in dicta, had noted that some courts in other states had questioned the continued vitality of the “open fields” doctrine, in light of the “legitimate expectation of privacy” test enunciated in Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967). Goehring dismissed those questions by reference to the post-Katz opinion in Air Pollution Variance Board v. Western Alfalfa Corp., 416 U.S. 861, 94 S.Ct. 2114, 40 L.Ed.2d 607 (1974), which referred to the “open fields” doctrine in upholding observations of air pollution. Moreover, both Goehring and Katz were handed down before Oliver and Dunn, which both expressly relied on the “open fields” doctrine. Appellant’s contention is without merit. See also Ochs v. State, 543 S.W.2d 355 (Tex.Crim.App.1976), cert. denied, 429 U.S. 1062, 97 S.Ct. 786, 50 L.Ed.2d 778 (1977); Beasley v. State, 683 S.W.2d 132 (Tex.App. — Eastland 1984, pet. ref’d); Hurwitz v. State, 673 S.W.2d 347 (Tex.App — Austin 1984), aff'd on other grounds, 700 S.W.2d 919 (Tex.Crim.App. 1985).
Appellant also questions the knowing and voluntary nature of his consent to search the ranch, once the officers had entered. Appellant contends that he only finished the sixth grade while living in Mexico, that he speaks very little English, and that he was confronted by several armed law enforcement officers. Under these circumstances, argues appellant, his apparent consent to search the premises merely amounted to a submission to a claim of lawful authority. See Meeks v. State, 692 S.W.2d 504, 509 (Tex.Crim.App.1985); Clemons v. State, 605 S.W.2d 567, 571 (Tex.Crim.App.1980); Paprskar v. State, 484 S.W.2d 731, 737 (Tex.Crim.App.1972).
Meeks v. State, 692 S.W.2d at 509-10, clearly sets out the standards for determining whether a defendant has waived his or her right, under the fourth amendment to the U.S. Constitution and article I, section 9, of the Texas Constitution, to be free from unreasonable searches and seizures. The State has the burden of proving by clear and convincing evidence that consent was given freely and voluntarily and that the consent given was positive and unequivocal, free from duress or coercion, either actual or implied. This burden cannot be discharged by showing nothing more than acquiescence to a claim of lawful authority. Such submission renders the search invalid. Whether a consent to search was voluntary presents a question of fact that must be determined from the totality of the circumstances.
In the first place, appellant’s argument has only limited support in the record. No evidence was presented of the extent of appellant’s education. Although he testified through an interpreter at trial, he told Officer Escalón at the scene of the arrest that he spoke English “fairly well.”
Officer Escalón, at the hearing on the motion to suppress, testified that he told appellant he suspected the tractor trailer on the ranch contained marihuana. He continued as follows:
Q. What did you do next?
A. Then, I read him his rights, I sat him in the car. It was cold. I sat him in the car, and I talked to him as to why we were there. As far as the consent of the search, he was very cooperative, and that’s when he signed the consent (form).
Q. Did you, in any way, tell him as to whether or not he gave consent, giv*907ing you consent to search that trailer?
A. I did tell him that the place was going to be searched, either by his consent, or that later, we would come back and check the place.
Q. All right. And was he cooperative?
A. Yes, sir, he was.
Q. Was he very cooperative?
A. I would say very cooperative, yes, sir.
Appellant then stated that he had the keys to the padlock on the tractor trailer. After signing the written consent form, appellant walked over and opened the padlock for the officers. Escalón also testified that appellant was twice given his rights, in English and in Spanish, and that appellant was “very cooperative.” No other witnesses testified on the issue of consent.
At trial, Officer Escalon’s testimony was the same. However, he added that, while the two were talking in the police car, appellant told him that there was marihuana in the tractor trailer. He even started to go open it up, but Escalón asked him to wait until he had written out the consent form.
The fact that a person is under arrest or in custody does not alone render a consent involuntarily given. It is merely one of the circumstances to be considered. United States v. Watson, 423 U.S. 411, 424, 96 S.Ct. 820, 828, 46 L.Ed.2d 598 (1976); United States v. Hall, 565 F.2d 917, 920 (5th Cir.1978); United States v. Jones, 475 F.2d 723, 729-30 (5th Cir.1973); Meeks, 692 S.W.2d at 510; Valerio v. State, 494 S.W.2d 892, 987 (Tex.Crim.App.1973). Nor is mere acquiescence to a claim of lawful authority to be inferred from the statement that the officers would get a search warrant if he did not consent. See United States v. Boukater, 409 F.2d 537, 538-39 (5th Cir.1969); Resendez v. State, 523 S.W.2d 700, 703 (Tex.Crim.App.1975); Stephenson v. State, 494 S.W.2d 900, 905 (Tex.Crim.App.1973). Viewing the evidence from the standpoint most favorable to the trial court’s determination, we hold that Officer Escalon’s testimony is sufficiently clear and convincing to establish the voluntariness of appellant’s consent. See Stephenson, 494 S.W.2d at 905.
Appellant also contends that no exigent circumstances existed to justify the officers’ warrantless search of the ranch. In view of our foregoing conclusion that appellant gave consent to search once the officers were lawfully on the premises, we need not address this point. Tex.R.App.P. 90(a).
Appellant contends, in his first point of error, that reversible error occurred in the trial court’s failure to sign a stipulation of evidence. Counsel for appellant and the State stipulated on the record that, if a certain chemist from the Texas Department of Public Safety testified, he would testify that the substance he tested was marihuana, and that it weighed 617 pounds. No written agreement to stipulate or consent to waive his right to confront witnesses appears in the record.
Tex.Code Crim.Proc.Ann. art. 1.15 (Vernon 1977) is a mandatory statute requiring that an agreement to stipulate evidence, and a waiver of the appearance, testimony, and confrontation of a witness, must be written and must be approved by the court. It is the consent and waiver which must be approved, not the stipulation itself. McClain v. State, 730 S.W.2d 739 (Tex. Crim.App.1987); Messer v. State, No. 570-84 (Tex.Crim.App., April 1, 1987) (opinion on motion for rehearing) (not yet reported); Landers v. State, 720 S.W.2d 538, 540 (Tex. Crim.App.1986).
The State concedes that it did not comply with article 1.15, arguing instead that the “live” testimony presented the trial court with independently sufficient evidence to support the conviction. Our authority to consider such evidence is implicit in the cases cited above. E.g. McClain v. State, *908730 S.W.2d at 742-43.1 At trial, Escalón testified that he had been an agent of the Department of Public Safety for eighteen years. He later stated that he was familiar with and could identify marihuana. Escal-ón also testified that he saw a white package being placed in the trunk of the orange Trans Am which had backed up to the tractor trailer. The packages were wrapped in the manner which marihuana is often packaged. After the Trans Am left the ranch, Escalón stopped it and discovered “several packages or bundles that appeared to be marihuana.” He later stated that, in his opinion, those several packages contained about eighty pounds of marihuana. Escalón then testified that, when he searched the tractor trailer, he found “similar bundles of what appeared to be marihuana towards the front of the trailer bed” (emphasis added). Approximately fifty-four of these bundles were recovered from the tractor trailer. On cross-examination, he also testified that, based on his training, marihuana was seized from the Trans Am, and it was packaged the same as the “stuff” he later seized at the ranch.
Based on this testimony, the trial court, as trier of fact, could have determined from all of this evidence that, if the “several” packages in the Trans Am’s trunk to-talled near eighty pounds, then the fifty-four “similar bundles” of marihuana in the tractor trailer totalled between 200 and 2000 pounds, as alleged in the indictment. We hold that this independent evidence was sufficient to support the conviction without the proper written stipulation.
We have carefully considered all of appellant’s points of error, and they are overruled. The judgment of the trial court is AFFIRMED.
. In McClain, the Court of Criminal Appeals wrote,
"[A]ppellants’ convictions must be reversed because the evidence, which consists solely of the stipulations, is, without the stipulations, insufficient.... We hold that without the stipulated evidence, which is all of the evidence presented in the trial court, the evidence is insufficient to support the convictions.”