The cases are here on the defendants’ appeals under G. L. c. 278, §§ 33A-33G, following their convictions for unlawful possession of heroin. The defendants have waived all but one of five assignments of error, leaving for our consideration only their contention that the judge improperly denied defence motions to suppress certain items of real evidence seized pursuant to a search warrant. The defendants’ argument raises an important question concerning the construction of the statutes which govern the time limits within which search warrants must be executed and returned to court (G. L. c. 276, §§ 2A and 3A 2 ).
We need summarize only that evidence which is pertinent to the judge’s ruling on the motions to suppress. On November 30,1971, a member of the Boston police department obtained from the Municipal Court of the Roxbury District a warrant to search a designated dwelling located *521 in Boston. On December 7,1971, at 11 p.m., several officers, pursuant to the search warrant, conducted a search of the premises. In the course of that search the police discovered and seized a quantity of heroin and various other items which the police characterized as paraphernalia associated with the processing of heroin for sale. The defendants were on the premises where the heroin was found and were arrested. The police returned the search warrant to the issuing court on December 8,1971.
At the hearing on the defendants’ motions to suppress, there was testimony by one of the defendants and by two of the police officers who had participated in the search. There was no inquiry into, and no explanation of, the seven-day delay between the issuance and the execution of the search warrant. Subsequent to the hearing the judge issued findings, rulings and order in which he stated that there had been no evidence introduced to explain the seven-day delay. He ruled that the “immediate search” requirement of § 2A had not been met and that the warrant had not been returned within seven days as required by § 3A, and he therefore ordered that the defendants’ motions to suppress be allowed. Subsequently the judge allowed the Commonwealth’s motion for a rehearing and, without hearing further testimony, vacated his prior order and ordered that the motions to suppress be denied. That final order is the subject of these appeals. The principal issue presented is whether a search conducted seven days after issuance of the warrant authorizing it satisfies the “immediate search” requirement of § 2A. 3
*522
The meaning of “immediate” is nowhere defined in the statutes controlling the issuance and execution of search warrants, G. L. c. 276, §§ 1-7, and it is not easily translated into any particular time limitation which would establish a single standard of immediacy to govern every case. Other courts, confronted with statutes or court rules which require “immediate” or “forthwith” service of warrants, have construed such terms as requiring service within a “reasonable” time. See, e.g.,
Spinelli
v.
United States,
The Commonwealth argues that the seven days allowed for return of a search warrant (§ 3A) should be read as evidence of a legislative purpose to permit seven days for the execution of warrants as well. Thus, according to that argument, any search pursuant to a warrant which has been conducted within seven days of issuance of the warrant would be presumptively reasonable, and there would be no burden on the prosecution to show justification for any delay up to seven days. There is nothing, however, on the face of either statutory provision-which compels the inference that the Legislature intended the seven-day deadline for return of warrants to apply to execution of warrants as well. Nor has any Massachusetts case come to our attention in which this issue was considered. There are, however, a number of Federal cases dealing with a somewhat similar question.
Prior to a 1972 amendment, the Federal Rules of Criminal Procedure contained two provisions analogous to G. L. c. 276, §§ 2A and 3A. Rule 41 (c) of the Federal Rules of Criminal Procedure, 18 U. S. C. Appendix (1970), required
*523
that a search be made “forthwith” after issuance of the warrant. Rule 41 (d), however, required that a search warrant “may be executed and returned only within 10 days” of its issuance.
4
Many cases arose in the Federal Courts concerning the apparent conflict between the “forthwith” requirement of Rule 41 (c) and the ten-day limit of Rule 41 (d). Although no unanimity of decision was achieved, several distinct lines of interpretation did appear. A few courts held that the ten days permitted by Rule 41 (d) defined the meaning of “forthwith” in Rule 41 (c) so that execution of a search warrant any time within ten days of issuance was per se reasonable. See, e.g.,
Mitchell
v.
United States,
The context in which the foregoing decisions were made is not precisely the same as the statutory context of our cases: the two Federal rules both purported to set time limits on the execution of search warrants; on the other hand, only one of the Massachusetts statutes sets a time limit on execution of search warrants (“immediate” — § 2A), while the other statute sets a time limit only on the return of search warrants (“not later than seven days” — § 3A). Thus, we do not have any direct statutory conflict to resolve. Nevertheless, we believe that the construction adopted in the line of Federal cases last referred to above suggests the proper resolution of the issue before us.
In the first place, because a warrant cannot be executed after it has been returned to court, and because § 3A requires return of a search warrant within seven days, we think that it is logical to infer from § 3A a legislative judgment that warrants must be executed, as well as returned, within seven days. Therefore, we hold that no search warrant may validly be executed more than seven days after its issuance. Cf.
Sgro
v.
United States,
. This does not mean, however, that execution of a search warrant any time within seven days of its issuance will necessarily be reasonable. A search warrant may issue only when facts are presented to a magistrate which show probable cause that relevant evidence will be found at a designated location. The longer the police wait before executing the warrant, however, the more likely it is that the situation will change so that the facts which supported the magistrate’s determination of probable cause will no longer exist. See
United States
v.
Wilson,
60 F. R. D. 55, 57-58 (E. D. Mich. 1973). The likelihood that circumstances will change is especially high where the object of the search is any easily moved substance, such as narcotics.
Ibid. “A
warrant is issued upon allegation of presently existing
*525
facts, and as such does not allow execution at the leisure of the police, nor does it invest the police officers with the discretion to execute the warrant at any time . . . believed by them to be the most advantageous.”
Spinelli
v.
United States,
However, even if the delay in executing a search warrant in a particular case is found to have been unreasonable, evidence seized pursuant to that search warrant need be suppressed only if the defendant can demonstrate that he suffered legal prejudice as a result of the delay. “The fact that the search uncovered prejudicial evidence does not invest standing unless the presence of the evidence is attributable to the delay.”
Spinelli
v.
United States, supra,
at 886. See
House
v.
United States,
To summarize, we hold that G. L. c. 276, § 2A, requires execution of search warrants within a reasonable time after issuance. Execution of a search warrant which is delayed more than seven days is per se invalid without regard to *526 prejudice. Even if a delay of no more than seven days is shown to be unreasonable, evidence seized pursuant to the warrant need be suppressed only if the defendant sustains the burden of proving legal prejudice attributable to the delay. In the cases now before us, the defendants have made no showing of such prejudice, and the denial of their motions to suppress must therefore be affirmed.
Judgments affirmed.
Notes
“Section 2A. The warrant shall be in substantially the following form:
THE COMMONWEALTH OF MASSACHUSETTS.
(County), ss. (Name) Court.
To the Sheriffs of our several counties, or their deputies, any State Police Officer, or any Constable or Police Officer of any city or town, within our said Commonwealth.
Proof by affidavit having been made this day before (name of person authorized to issue warrant) by (names of person or persons whose affidavits have been taken) that there is probable cause for believing that (certain property has been stolen, embezzled, or obtained by false pretenses; certain property is intended for use or has been used as the means of committing a crime; certain, property has been concealed to prevent a crime from being discovered; certain property is unlawfully possessed or kept or concealed for an unlawful purpose).
W e therefore command you in the daytime (or at any time of the day or night) to make an immediate search of (identify premises) (occupied by A. B.) and (of the person of A. B.) and of any person present who may be found to have such property in his possession or under his control or to whom such property may have been delivered, for the following property: (description of property) and if you find any such property or any part thereof to bring it and the persons in whose possession it is found before (court having jurisdiction) at (name of court and location).
Dated at (city ortown) this day of ,19 .
Clerk.”
“Section 3A. Every officer to whom a warrant to search is issued shall return the same to the court by which it was issued as soon as it has been served and in any event not later than seven days from the date of issuance thereof, with a return of his doings thereon; provided, however, that a justice of the superior court may at any time receive complaints and issue search warrants returnable in seven days before a district court named in such warrant and in that event the officer shall make his return to such district court as directed.”
Two other related issues may quickly be disposed of. First, the execution of the warrant in this case was within seven days of its issuance only if the day of issuance is not counted. It is generally held that the day from which a time period is to be computed is not counted in the computation of the period.
Daley
v.
District Court of Western Hampden,
Rule 41 was revised in 1972, 18 U. S. C. Appendix (Supp. II, 1972). It now provides that a search warrant must state on its face the duration of its validity (up to ten days).
The safety of the police officers who execute warrants would clearly constitute one consideration which might justify delay. See
United States
v.
Rael,
