The defendants filed motions to suppress evidence obtained by the State police acting pursuant to a search warrant issued by a judge of the Superior Court. The defendants, each of whom was charged with violations of the gaming laws, contended in support of their motions that the affidavit on which the search warrant was issued was insufficient to permit a finding of probable cause under the "two-pronged” test of
Aguilar
v.
Texas,
The affidavit on which the search warrant was issued was signed by a State police officer. The affidavit disclosed that an unknown informant, who declined to reveal his name, had told another officer of the State police of two gambling operations. One was conducted at a spa in Somerville; the other was conducted at the location to which a particular telephone number was listed. The police determined that the telephone number was listed to certain premises in Medford, for whose search the warrant in this case was issued.
The information in the affidavit concerning the Somerville spa was substantial. The informant had given detailed facts concerning the gambling operations conducted at the spa and the person engaged in them. The officer who signed the affidavit conducted an extensive investi *78 gation of activities at the spa. He entered the spa on four occasions and observed conduct which was consistent with the operation of illegal betting on the premises. A separate search warrant was issued for the search of the spa, and the propriety of the issuance of that warrant is not before us.
The informant’s disclosure of information concerning gambling operations at the Medford address and the officer’s corroboration of that information were far less extensive. The affidavit stated that the unknown informant had said that a specific telephone number was being used for accepting gambling wagers by a person known to him as Richard Alessio and by another man unknown to him. Alessio had told the informant that the telephone number was unpublished and listed in the name of a relative to avoid detection. The informant said that "he had placed gaming wagers at this telephone number within one (1) week” of his disclosure to the State police. The officer checked the telephone number and found that it was unpublished and listed to "John Alessi” at the location in Medford.
On September 14, 1976, the officer observed the Med-ford premises, and from approximately 11 a.m. to 12 m. he used a pay telephone about twenty-five times to dial the number listed to the premises. The line was always busy. At 12:10 p.m. the telephone was answered on the first ring by a male who said "Hi.” The officer said, "John,” the male said "Yeah,” and the officer hung up. On September 15, 1976, the officer again observed the premises, and dialed the number ten times between 11:30 a.m. and 11:50 a.m., always receiving a busy signal. Five minutes later the telephone was answered on the "first half-ring” by a man who said "Hi,” and the officer hung up. On September 22, 1976, the officer followed the same procedure, commencing at 11:20 a.m. He dialed the number approximately fifteen times during forty-five minutes and received a busy signal each time. At 12:10 p.m., the telephone was answered on the first ring by a man, and *79 a conversation took place which is set forth in the margin. 3 On September 30, 1976, starting at shortly before noon, the officer made similar attempts to call the number. Six times the number was busy. On three occasions the telephone was answered on the first ring by a man who said "Hi.” There was no significant conversation.
A search warrant may lawfully be issued by a magistrate only if there is a showing of probable cause for its issuance. When an unknown informant volunteers hearsay allegations on which the police seek a warrant, the affidavit in support of the application must inform the magistrate "of [1] some of the underlying circumstances from which the informant concluded that [criminal activity took place where he claimed it did] and [2] some of the underlying circumstances from which the officer concluded that the informant... was 'credible’ or his information 'reliable.’ ”
Aguilar
v.
Texas,
*80
1. The first "prong” of the
Aguilar
test is met. The affidavit sets forth underlying circumstances from which the magistrate could conclude that the informant had reliably determined that illegal bets were being registered at the premises which ultimately were searched. The informant had stated that "he had placed gaming wagers at [the specified] telephone number within one (1) week” prior to providing the police with his tip. The affidavit further disclosed that the telephone bearing that number was installed at the premises for whose search the warrant was issued. This information established the likelihood that illegal activity was occurring on the premises. See
Commonwealth
v.
Vynorius,
This case is to be distinguished from those in which the affidavit failed to disclose a sufficient underlying factual basis for the informant’s allegations that criminal activity had occurred. See, e.g.,
Commonwealth
v.
Stevens,
2. A closer question exists as to whether the affidavit adequately discloses underlying circumstances from which a magistrate could conclude that the undisclosed informant was credible or his information reliable, the second "prong” of the Aguilar test.
The judge below limited his consideration to matters stated in the affidavit concerning the premises to be searched. Therefore, he disregarded information concerning the Somerville spa. We think that the corroboration of the tip concerning illegal activities at the Somerville
*81
spa bears on the credibility of the informant and the reliability of the information he disclosed. The demonstrated reliability of an informant on matters other than the case before the court is, of course, relevant to the determination of the reliability of the informant. See
Commonwealth
v.
Boswell,
We believe that the informant’s reliability was supported further by the police observations of the Medford premises, considered in light of common knowledge concerning the methods of operation of entrepreneurs engaged in illegal gambling activities. See
Commonwealth
v.
Moran,
The defendants urge us to take account of the fact that the identity of the informant was unknown not only to
*82
the magistrate, but also to the police. Because of this anonymity, we do not attach substantial weight to the fact that the informant incriminated himself. See generally
Commonwealth
v.
Vynorius,
We believe that the magistrate was warranted in finding the informant to be reliable. We are concerned here with a determination of probable cause and not with guilt beyond a reasonable doubt. Good policy should allow "a certain leeway or leniency in the after-the-fact review of the sufficiency of applications for warrants.”
Commonwealth
v.
Corradino,
3. The orders of the trial judge allowing the defendants’ motions to suppress are reversed, and the case is remanded to the Superior Court for further proceedings.
So ordered.
Notes
In view of this conclusion, we need not decide whether the defendant MacLeod had standing to challenge the warrant to search premises owned by the defendant Alessio in which MacLeod was only a day visitor.
Unknown male: "Hi.”
Officer: "Hey, is this John?”
Unknown male: "Who’s this?”
Officer: "Dave, Dave Phillips from Somerville.”
Unknown male: "What do you want?”
Officer: "I just wanted to check is Gal Friday scratched at Suffolk.” Unknown male: "I don’t know you who gave you this number.” Officer: "A mutual friend he said not to use his name but it would be OK to call you.”
Unknown male: "I don’t talk to people I don’t know have him call me and you can call him.”
Officer: "OK.”
At this point the officer hung up without any further conversation.
The affidavit stated that "Gal Friday” was a horse scheduled to run that day at a local race track.
