¶1
Brown, J.— Denise Merkt was arrested after police, executing a search warrant, found methamphetamine and drug paraphernalia in her vehicle and in a residence she occupied in Benton County. She appeals the trial court’s denial of her motion to suppress evidence obtained as the result of the allegedly illegal search warrant. We affirm.
FACTS
¶2 Richland Police Detective Eric Lundquist began watching a residence located at 1942 Luther in Richland, Washington, where Ms. Merkt allegedly lived. The detective was familiar with Ms. Merkt because in 1999 and 2000 her former neighbors complained about suspiciously heavy traffic coming and going at all times of the day and night from her residence. In September 2001, the detective received new information that Ms. Merkt was selling illegal drugs from the residence on Luther. The detective drove past the Luther residence on at least 20 to 25 different occasions between September 2001 and April 2002 to watch for signs of drug activity. Ms. Merkt’s vehicle was nearly always present at different times during both daytime and evening hours. The detective contacted Amy Simpson at the Luther address on September 19, 2001. Ms. Simpson admitted Ms. Merkt was her roommate.
¶3 In January 2002, informant Doug Turner, a convicted felon, contacted Detective Lundquist offering to provide *611information regarding drug activity in Richland in exchange for help on a pending driving while under the influence charge. The detective told Mr. Turner no deals could be made. Mr. Turner told the detective he was a methamphetamine user tired of the effect it was having on his life. Mr. Turner directed the detective to 1942 Luther. He told the detective “Denise” lived there and sold “dope” out of that location. Clerk’s Papers at 57. He said he had received methamphetamine from Denise at that location and had been present when her supplier brought drugs needing to be sold to the residence. Mr. Turner did not know Denise’s last name, but knew she drove a blue-colored minivan. Detective Lundquist already knew Ms. Merkt had a blue minivan registered in her name. Mr. Turner told the detective he had been at the Luther residence many times and there were always drugs there. Mr. Turner said he had not been to the Luther residence since December 2001.
¶4 The detective independently learned Ms. Merkt’s van was driven to a Rite Aid store in Richland on January 26, 2002, where a man and woman each purchased the maximum amount of pseudoephedrine products allowed by law. From his training and experience, the detective knew that the over-the-counter medicine was often used in the manufacture of methamphetamine and could be traded by the purchaser to a methamphetamine cook for a small amount of the finished product.
¶5 On March 25, 2002, Detective Lundquist met with informant Brett Wilder, an inmate at the Benton County jail. Mr. Wilder wanted to talk with the detective about drug activity in the Tri-Cities. Although Mr. Wilder asked for favorable treatment in exchange for the drug information, the detective told him no deals could, or would be made. Mr. Wilder then told the detective a woman named Denise Merkt, who lived on Luther, sold dope. Mr. Wilder said he had last purchased dope from Denise during the first week of March 2002. He also said he could purchase dope from her at any time.
*612¶6 On April 1, 2002, Detective Lundquist applied for, and received, a warrant allowing him to search the residence at 1942 Luther, as well as Ms. Merkt’s vehicle and person. Based on evidence gathered as a result of the search, Ms. Merkt was charged with unlawful possession of a controlled substance, maintaining a dwelling for controlled substances, and criminal mistreatment in the second degree.
¶7 Ms. Merkt unsuccessfully moved to suppress evidence based on an allegedly defective search warrant. Ms. Merkt was found guilty by a jury solely of the possession and mistreatment charges. After a standard range sentencing, Ms. Merkt appealed.
ANALYSIS
¶8 The issue is whether the trial court erred in denying Ms. Merkt’s motion to suppress.
¶9 A search warrant must be based upon probable cause. State v. Cole, 128 Wn.2d 262, 286, 906 P.2d 925 (1995). A search warrant probable cause decision is reviewed for abuse of discretion. State v. Anderson, 105 Wn. App. 223, 228, 19 P.3d 1094 (2001). Great deference is given to the court’s decision. Id. “All doubts are resolved in favor of the warrant.” Id. We consider solely the information provided the issuing magistrate. Id. at 229.
¶10 A search warrant application must specify the underlying facts so the magistrate can make a detached and independent assessment of the evidence. State v. Thein, 138 Wn.2d 133, 140, 977 P.2d 582 (1999). Probable cause exists if the affidavit for a search warrant sets out facts and circumstances sufficient to establish a reasonable inference the defendant is probably involved in criminal activity and that evidence of the particular crime will be found in the place to be searched. Id. Mere speculation or an officer’s personal belief will not suffice. Anderson, 105 Wn. App. at 229. An affidavit of probable cause must show “a nexus between criminal activity and the item to be seized, and *613also a nexus between the item to be seized and the place to be searched.” Thein, 138 Wn.2d at 140.
¶11 When the probable cause affidavit is based on an informant’s hearsay, it must show the informant is probably trustworthy and has personal knowledge regarding the facts asserted under Aguilar-Spinelli1 Under Aguilar-Spinelli, the informant’s statements are tested by the familiar two-pronged test, (1) credibility/reliability and (2) basis of knowledge. The credibility prong may be satisfied by an informant’s track record, if any, or by showing the informant was acting against his penal interest. State v. Jackson, 102 Wn.2d 432, 437, 688 P.2d 136 (1984). The basis of knowledge prong may be satisfied if the informant has personally witnessed the facts asserted. Id. Here, the basis of knowledge prong is uncontested.
¶12 The existence of probable cause is tested in a commonsense fashion. State v. Jackson, 150 Wn.2d 251, 265, 76 P.3d 217 (2003). If an affidavit does not establish probable cause, a defense motion to suppress evidence seized as a result of an improper warrant should be granted. Anderson, 105 Wn. App. at 229.
¶[13 The probable cause affidavit supports the magistrate’s decision to issue the search warrant. The detective knew from his investigation and prior contacts with Ms. Merkt that she associated with Danny Hunter, a well known local methamphetamine cook. Detective Lundquist knew Ms. Merkt had two previous felony drug convictions. Detective Lundquist had spoken with Ms. Simpson, who admitted Ms. Merkt lived at 1942 Luther. Detective Lundquist monitored the absence or presence of Ms. Merkt’s blue minivan at that residence. Details surrounding the informal surveillance were flushed out at trial but were sufficiently revealed to the magistrate.
¶14 Both informants, Mr. Turner and Mr. Wilder, gave statements against their penal interests, thus establishing *614the reliability of their information as discussed in State v. Lair, 95 Wn.2d 706, 710-11, 630 P.2d 427 (1981) and Jackson, 102 Wn.2d at 437. They voluntarily agreed to speak with the detective in spite of the detective’s refusal to make any deals and gave incriminating evidence against Ms. Merkt and themselves. That an informant is named is one fact the court considers in determining the sufficiency of an affidavit of probable cause. State v. Duncan, 81 Wn. App. 70, 78, 912 P.2d 1090 (1996). Significantly, while making statements against their penal interests, both witnesses volunteered critical evidence that linked Ms. Merkt to illegal drug activity occurring at the Luther address. These informants provided first-hand knowledge of purchases. Thus, both Aguilar-Spinelli prongs are satisfied.
¶15 Finally, Ms. Merkt infers the information provided in the affidavit was stale. The test for staleness is common sense. State v. Hall, 53 Wn. App. 296, 300, 766 P.2d 512 (1989). To determine whether information is stale, we review a number of factors, which include (1) the amount of time that has elapsed and (2) the nature and scope of the suspected activity. Id. Here, one witness had purchased illegal drugs about four months prior to the search warrant issuing and the other approximately one month prior.
¶16 Ms. Merkt had a past criminal drug history. The witnesses’ voluntary statements to Detective Lundquist corroborated each other. Ms. Merkt’s vehicle was used to purchase large amounts of a drug precursor approximately three months prior to the search. While a single piece of information, viewed in isolation, might have been considered stale, the totality of the information established probable cause that the drug sales were current and ongoing. The trial court did not abuse its discretion in deciding the information taken together in a commonsense fashion was not stale. We defer to the trial court’s decision *615and resolve doubts in favor of the warrant. Anderson, 105 Wn. App. at 229.
¶17 Affirmed.
Sweeney, A.C.J., concurs.
Spinelli v. United States, 393 U.S. 410, 89 S. Ct. 584, 21 L. Ed. 2d 637 (1969); Aguilar v. Texas, 378 U.S. 108, 84 S. Ct. 1509, 12 L. Ed. 2d 723 (1964).