Opinion
MOSK, J.We granted review in this case to determine whether the Los Angeles Police Department (LAPD) should be enjoined from using a motorized battering ram and pyrotechnic explosive devices known as “flash-bangs” to execute searches of so-called “rock houses,” which are specially fortified residential dwellings where crystallized “rock” cocaine is made and sold. As will appear, we are persuaded that the unregulated use of the motorized battering ram, but not the flashbangs, poses a significant and unusual threat to property and public safety that may, unless subject to judicial scrutiny, contravene the proscription against unreasonable searches contained in the Fourth Amendment to the United States Constitution and article I, section 13, of the California Constitution.
In light of the deliberate, often prolonged, planning that the LAPD undertakes before it deploys the device, prior judicial review of its proposed use of the ram against suspected rock houses is unlikely to obstruct effective law enforcement. Therefore we conclude that a writ of mandate should issue directing the trial court to enjoin deployment of the ram to execute search or arrest warrants unless a magistrate authorizes its use, and unless exigent circumstances arise at the time of entry. On the other hand, since we are not convinced that the flashbangs are inherently dangerous, we rely on the discretion of law enforcement agencies to determine when and under what circumstances they are to be used.
Petitioners (hereinafter plaintiffs) are taxpayers and individuals who occupied a suburban Los Angeles residence on the evening of February 6, 1985, when it was forcibly entered by LAPD officers using a motorized battering ram to penetrate a wall of the house and flashbangs to divert and disarm its occupants. The police were executing a search warrant issued several days earlier after an informant made a controlled purchase of rock cocaine through a metal slot in the front door.
The LAPD had engaged the assistance of Special Weapons and Tactics Team members to break into the house, after concluding that iron bars over its windows and an electronically controlled locked “cage” at the front *25entrance precluded rapid entry by less dramatic means. The police chief invited the news media to witness the first use of the “V-100,” an armored personnel carrier equipped with a battering ram. In front of television cameras and without prior warning to the occupants—other than a bystander’s shouts of “Police!”—the officers drove the ram through the exteri- or wall of the house and into a family room; simultaneously, police detonated flashbangs in the room and entered in full force. As it turned out, the house was occupied by two unarmed women and their three young children; the officers recovered no weapons and only trace amounts of cocaine along with alleged drug paraphernalia.
Plaintiffs brought an action for damages and declaratory and injunctive relief on federal and state grounds, contending that the LAPD’s practice of using the motorized battering ram and flashbangs against residences constitutes inherently excessive force which is unreasonable per se under the Fourth, Fifth, Ninth, and Fourteenth Amendments of the United States Constitution, and article I, sections 1, 7, 13, and 15 of the California Constitution. Real parties in interest (hereinafter defendants) removed the action to federal court, which remanded to state courts all claims with the exception of a damage action under a federal civil rights statute. By then—in May 1985—the LAPD had used the devices in a total of four searches of suspected rock houses.
Plaintiffs applied for a preliminary injunction, urging that the ram and flashbangs be prohibited in searches of occupied dwellings. At the hearing, however, they stipulated that they did not seek to restrict LAPD deployment of either device “if such use reasonably appears necessary to stop an ongoing threat of immediate serious injury or death” such as in a terrorist or hostage scenario.
Defendants responded that the use of the devices was entirely justified by the unique problems for law enforcement posed by the fortress-like rock houses proliferating in residential areas. Rock houses are typically equipped with steel bars on exterior windows and are entered by way of multiple steel doors: a mesh entry door provides access to a barred “cage,” and a second steel-reinforced door may lead from there to the interior of the house or to a third door that is the actual front door. Officers can usually only surmise the extent of interior hardware, which may include steel bars and mesh over windows on the inside of the house, multiple deadbolts on interior and exterior doors, and thick boards bolted across entries. Even approaching such operations may be dangerous to law enforcement officers as rock houses may monitor outside activity by means of cameras and other electronic surveillance devices.
*26Defendants averred that the fortifications of the house in question appeared more elaborate than those installed on other houses in the neighborhood to avert burglaries—although they conceded their preliminary investigation was hampered because their informant could not see into the interior of the house. The informant’s purchase of cocaine confirmed LAPD suspicions that it was a rock house: the informant was “buzzed” into the front cage, the exterior door of which was locked after entry, he exchanged cash for rock cocaine through the door slot, and he was released after being “buzzed” out. Furthermore, raids against two similarly fortified houses owned by the same individual suspected of owning the target house had yielded cocaine and weapons, and neither had contained clothing or furnishings indicating the presence of regular occupants.
On the basis of the 2 previous raids and of the statistically high incidence of weapons in rock houses generally—between October 1984 and February 1985, police seized 207 guns in 269 operations against such houses—the LAPD anticipated armed resistance. Moreover, because of the elaborate ironworks of the exterior entrances, they concluded it would be impossible to enter by conventional methods before evidence was destroyed.
Defendants went on to describe the engines of war that are the subject of the present action. Each V-100 armored personnel carrier is mounted with a 14-foot horizontal steel pole capped with a rectangular steel plate. Driven at approximately five miles an hour against the exterior wall of a building and then withdrawn, it creates a hole large enough for several officers to enter simultaneously. Although approved by the department for use in nine raids, the motorized rams have actually been deployed only four times, with no physical injuries to persons or major damage to buildings, either stucco or brick. Plaintiffs contended this apparent safety record is misleading, warning that according to their experts structural damage could be catastrophic, resulting in serious injuries through flying debris, collapsed ceilings, and even explosion and fire.
Defendants asserted that flashbangs have proved particularly effective in safely disarming dangerous individuals, by temporarily blinding them with a brilliant flash of light and confusing them with artillery-like sounds. Since they were introduced into the police arsenal in 1982, flashbangs have been approved by the department for use 38 times, on 25 occasions in 1985 alone. Defendants introduced expert testimony showing that flashbangs are designed exclusively to produce dramatic pyrotechnics, not to injure, and should cause only minor skin bums at worst. This has proved true, with a single tragic exception: a woman was killed in December 1984 when a flashbang exploded between her back and a wall. The LAPD accounts the death a “freak” accident, but has taken measures to preclude a similar *27mishap by reducing by half the explosive power of the device and requiring that officers detonate them only after they have seen fully into a target area. No other injuries have been reported.
Defendants maintained that although dangerous, the devices do not constitute deadlier force than many of the conventional tools—including tear gas, hand-held battering devices, and explosives applied directly to deadbolts—long used for forcible entry. They argued that a blanket prohibition against a particular device, subject to magistrate approval, is without precedent. Moreover, such review would duplicate the careful prior screening already conducted by police administrative panels, which approve deployment only when either device is the safest means of accomplishing a speedy forced entry. Finally, they insisted that injunctive relief is unavailable: courts may review the LAPD’s use of any particular weaponry only retrospectively, on a case-by-case basis.
The trial court agreed with defendants. It denied plaintiffs’ motion for injunctive relief concluding that although they might eventually establish that the motorized battering rams and flashbangs are unreasonable per se, they had submitted insufficient data to demonstrate a current policy of misuse by the LAPD. It observed that short of banning the devices outright, it lacked authority to regulate or condition their use except by requiring prior judicial authorization for nighttime service.
Although it denied the motion on the ground that “it’s a mistake for the court to interfere in the first instance,” the court expressed misgivings about use of the motorized battering ram without judicial oversight: “Waking people after 10 o’clock you have to get the magistrate’s permission. Knocking a large hole in a wall of a residence where people might be sleeping, you don’t have to get a magistrate’s permission.” It “question[ed] the wisdom” of LAPD policy, urging “The judgment having been made to use the ram, why can’t you tell the magistrate on an honest basis that this is a situation that calls for the battering ram and we are seriously contemplating it?”
Plaintiffs petitioned the Court of Appeal for a writ of mandate to compel the trial court to grant preliminary injunctive relief. The Court of Appeal summarily denied the petition on the ground that plaintiffs have an adequate remedy by appeal. We granted plaintiffs’ petition for review and issued an alternative writ of mandate. In so doing we necessarily determined that plaintiffs lack a “plain, speedy, and adequate remedy in the ordinary course of law.” (Code Civ. Proc., § 1086; see Robbins v. Superior Court (1985) 38 Cal.3d 199, 205 [211 Cal.Rptr. 398, 695 P.2d 695].)
*28A trial court’s decision to deny provisional relief is discretionary and will be upheld if it is supported by sufficient evidence, even if there is evidence that could support a contrary conclusion. (See Nestle v. City of Santa Monica (1972) 6 Cal.3d 920, 925-926 [101 Cal.Rptr. 568, 496 P.2d 480].) A writ of mandate will issue to control the exercise of judicial discretion only when a court has acted capriciously or “where, under the facts, that discretion can be exercised in only one way.” (Babb v. Superior Court (1971) 3 Cal.3d 841, 851 [92 Cal.Rptr. 179, 479 P.2d 379]; Robbins v. Superior Court, supra, 38 Cal.3d 199, 205.)
In deciding whether a preliminary injunction should issue, the trial court must evaluate two interrelated factors: “The first is the likelihood that the plaintiff will prevail on the merits at trial. The second is the interim harm that the plaintiff is likely to sustain if the injunction were denied as compared to the harm that the defendant is likely to suffer if the preliminary injunction were issued.” (IT Corp. v. County of Imperial (1983) 35 Cal.3d 63, 69-70 [196 Cal.Rptr. 715, 672 P.2d 121]; accord, Cohen v. Board of Supervisors (1985) 40 Cal.3d 277, 286 [219 Cal.Rptr. 467, 707 P.2d 840].) Our inquiry into whether the court abused its discretion in the present case is therefore two-fold: do plaintiffs demonstrate they are likely to prevail on the merits of their challenge to the LAPD’s current practice of using motorized battering rams and flashbangs? And are they likely to suffer irreparable harm to their interests as individuals and as taxpayers if interim relief is withheld?
We conclude that plaintiffs fail to meet the foregoing requirements as to the flashbangs. We are not persuaded by their claim that flashbangs, like the ram, pose an unacceptable threat to property and person. At their present reduced explosive power, and under current LAPD guidelines requiring that officers detonate them only after they have seen fully into a targeted room, the flashbangs appear from the record to present a minimal risk of injury—certainly a lesser risk than the use of guns to disarm hostile suspects. Flashbangs have been used without incident under the modification and restrictions instituted by the LAPD in 1984 after a single fatal accident; in more than 25 cases since 1984, the flashbangs have aided the police while inflicting only momentary disorientation on suspects. Because use of the flashbangs may not, therefore, be accounted unreasonable, the court did not abuse its discretion in denying a preliminary injunction against their use.
The motorized battering ram, however, presents a more difficult problem. We first address the merits of plaintiffs’ underlying claim that prior judicial authorization is required before officers use the battering ram, which is a destructive and dangerous means of forcible entry into an occupied dwelling.
*29Although defendants dispute the level of risk posed by the V-100 battering ram, they concede the potential danger from collapse of building walls and ceilings or through rupture of utility lines. Fire from damaged electrical wires or explosion from gas leaking from broken gas pipes could threaten the safety not only of occupants, but of entire neighborhoods. Because of the unprecedented risks to owners, occupants, and neighbors of suspected rock houses, therefore, routine deployment of the ram to enter dwellings must be considered presumptively unreasonable unless authorized in advance by a neutral magistrate, and unless exigent circumstances develop at the time of entry.
Defendants insist that short of an absolute ban on devices deemed unreasonable per se, judicial review of police tactics is limited to after-the-fact inquiry into whether the force used was excessive. We disagree. Although we have not previously imposed specific conditions on the use of any single weapon in the police arsenal, there is authority for requiring magistrate approval for especially dangerous and intrusive law enforcement practices. Penal Code section 1533, for example, permits nighttime service of an arrest or search warrant only on a showing of good cause and at a magistrate’s discretion. Similarly, this court held that certain intrusive body searches without special warrant are presumed unreasonable even when performed incident to a valid arrest and on probable cause. (People v. Scott (1978) 21 Cal.3d 284 [145 Cal.Rptr. 876, 578 P.2d 123].) Common to both limitations is the concern that the sensitive evaluation of unusual and dangerous intrusions affecting privacy and security interests of targeted persons should not be left exclusively to the “officer engaged in the often competitive enterprise of ferreting out crime.” (Johnson v. United States (1948) 333 U.S. 10, 13-114 [92 L.Ed.2d 436, 440, 68 S.Ct. 367].) Although searches of rock houses are directed against residences and not persons, the risk of incidental injury to human beings within the residences is reasonably foreseeable.
Defendants insist that the Fourth Amendment imposes no requirement of judicial oversight: “it is generally left to the discretion of the executing officers to determine the details of how best to proceed with the performance of a search authorized by warrant—subject of course to the general Fourth Amendment protection ‘against unreasonable searches and seizures.’ ” (Fn. omitted.) (Dalia v. United States (1978) 441 U.S. 238, 257 [60 L.Ed.2d 177, 192, 99 S.Ct. 1682].) Their reliance on Dalia is misplaced.
First, Dalia is distinguishable on its facts. It involved a warrant authorizing a telephone wiretap under 18 United States Code section 2518, and addressed the limited question of whether a separate warrant was required before federal officers could enter a business office covertly to install the device. The court found such authorization implicit in the original warrant: *30in virtually every wiretap, surreptitious entry is necessary and a separate warrant would prove an “empty formalism.” (Id., at p. 258 [60 L.Ed.2d at p. 193].) Second, covert entry involves minimal destruction of property and danger to persons; as the court noted, it is generally the safest—and often the only—means of executing a legal wiretap. On those grounds, the court held that covert entry is a reasonable means of executing a warrant for electronic eavesdropping.
Neither basis for the holding in Dalia applies here. Authority to make a forced entry by means of a powerful armed vehicle that smashes blindly through the walls of a residence is by no means implicit in a routine warrant to search for contraband. More important, the motorized battering ram is usually not the least destructive, safest, or only method of conducting such a search. Rather, it is so destructive that its use against residences generally infringes on occupants’ and owners’ rights to be secure against unreasonable searches and seizures.
Defendants insist we must defer in the first instance to police discretion. We do, in fact, yield to police discretion in the first instance as to the desirability of using mechanical force. But before such force is actually employed, the impartial judgment of a judicial officer must be interposed between citizens and the police. Thus the LAPD’s use of the V-100 battering ram must depend on prior magistrate approval.
Defendants next contend that in any case before-the-fact review is precluded by Parsley v. Superior Court (1973) 9 Cal.3d 934 [109 Cal.Rptr. 563, 513 P.2d 611], because the LAPD uses the motorized battering ram only under exigent circumstances that cannot be assessed in advance. In fact, however, the LAPD itself makes just such a prior assessment under its current procedures: it approves use of the ram in specific cases not because an exigent situation is in progress, but because it strongly suspects that when the officers arrive at the scene they will be met with resistance to a legal search.
In Parsley we held that the magistrate was without power to authorize noncompliance with the announcement requirement of Penal Code section 1531, which provides that an officer may break open any part of a house to execute a warrant “if, after notice of his authority and purpose, he is refused admittance.” We reasoned that failure to give notice could not be justified by the warrant provision alone: “the key to permissible unannounced entry is the knowledge of exigent circumstances possessed by police officers at the time of entry. Thus, from the viewpoint of a court reviewing justification for an unannounced entry after the fact, a warrant authorizing such action adds nothing.” (Id., at p. 940.) On the other hand, *31such a warrant would improperly allow the magistrate’s decision to substitute for the immediate determination of the situation officers face at the moment of entry. (Ibid.)
The same objections, however, do not apply to the type of prior authorization proposed here. The magistrate would not be asked to presume that the police will face an exigency at a rock house, nor would he require the LAPD’s actual deployment of the motorized battering ram: any use would still involve the threshold judgment of officers at the time of the search that an exigent situation had in fact developed—i.e., that evidence was in the process of being destroyed or that resistance to the search posed a serious danger of injury to police justifying deployment of the battering ram. It would not be sufficient to conclude that the objects named in the search warrant are by nature amenable to ready destruction or that occupants of rock houses are generally disposed to resist searches; a specific showing of exigency is needed. (See People v. Dumas (1973) 9 Cal.3d 871, 878-879 [109 Cal.Rptr. 304, 512 P.2d 1208]; People v. Gastelo (1967) 67 Cal.2d 586, 588-589 [63 Cal.Rptr. 10, 432 P.2d 706]; People v. Vollheim (1978) 87 Cal.App.3d 538, 543 [150 Cal.Rptr. 837].)
The magistrate should decide only whether the motorized battering ram could be used with relative safety against a particular building, if the need arises during execution of a search or arrest warrant. The LAPD declares that it already conducts its own screening of the need for the device and deploys it only as an extreme measure and only if officers at the scene remain convinced it is necessary. Magistrate review would simply place that screening, and the decision whether use of the ram could be justified, in the hands of a neutral and independent judicial officer.
In Scott we established a balancing test that we now adapt to the present case. (See 21 Cal.3d at pp. 293-294.) Before authorizing potential use of the battering ram, the magistrate finding probable cause for the underlying search must apply an additional balancing test to determine whether use of the device is appropriate. Factors that must be considered include the reliability of the ram under the specific circumstances as a rapid and safe means of entry, the seriousness of the underlying criminal offense and society’s consequent interest in obtaining a conviction, the strength of law enforcement suspicions that evidence of the crime will be destroyed, the importance of the evidence sought, and the possibility that the evidence could be recovered by alternative means less violative of Fourth Amendment protection. Alternative means include conventional methods of entry and such procedures as abatement against the owner of the suspected rock house or criminal charges under Health and Safety Code sections 11366 and 11366.5, which are especially tailored to combat the proliferation of fortified *32houses.1 All these considerations must, in turn, be balanced against the severity of the proposed intrusion: the likelihood of injury to innocent third parties as well as to occupants and police officers, and of extreme property damage to the target house and neighboring structures.
We conclude therefore that the motorized battering ram may be used in executing searches or arrests only after the LAPD satisfies three preliminary requirements: i.e., it (1) obtains a warrant upon probable cause, (2) receives prior authorization to use the ram from a magistrate, and (3) at the time of entry determines there are exigent circumstances amounting to an immediate threat of injury to officers executing the warrant or reasonable grounds to suspect that evidence is being destroyed.
Having concluded that plaintiffs are likely to prevail on the merits, we must now determine whether the balance of interim harm favors plaintiffs.
Plaintiffs are likely to suffer irreparable injury if the LAPD continues to deploy the motorized battering ram without prior judicial overview. There is danger of injury to persons and to property in any use of the device. Moreover, plaintiffs may claim injury as taxpayers for the expenditure of funds by the LAPD to execute searches by unlawful methods. (See Arrieta v. Mahon (1982) 31 Cal.3d 381, 387 [182 Cal.Rptr. 770, 644 P.2d 1249]; Blair v. Pitchess (1971) 5 Cal.3d 258, 269 [96 Cal.Rptr. 42, 486 P.2d 1242, 45 A.L.R.3d 1206].)
Defendants, on the other hand, cannot claim they will suffer comparable injury if they are enjoined from using the ram without prior judicial authorization. In light of their already extensive administrative review of proposed uses, the additional requirement that the magistrate issuing the search warrant also authorize possible use of the ram should be a minimal burden. The ability of law enforcement to respond to rapidly changing circumstances at the scene of the search will remain unimpaired.
*33For the foregoing reasons, we hold that the trial court abused its discretion in denying plaintiffs’ motion for a preliminary injunction. Let a peremptory writ of mandate issue directing respondent court to set aside its order of June 18, 1985, denying plaintiffs’ motion for a preliminary injunction in Langford et al. v. Gates et al., and to enter an order enjoining the use by defendants of their motorized battering ram unless they obtain prior judicial authorization to do so in a search or arrest warrant, and unless exigent circumstances arise at the time of entry.
Broussard, J., Grodin, J., and Reynoso, J., concurred.
Health and Safety Code section 11366 provides: “Every person who opens or maintains any place for the purpose of unlawfully selling, giving away, or using any controlled substance . . . which is a narcotic drug classified in Schedule III, IV, or V, shall be punished by imprisonment in the county jail for a period of not more than one year or the state prison.”
Section 11366.5, subdivision (b) states: “Any person who has under his or her management or control any building, room, space, or enclosure, either as an owner, lessee, agent, employee, or mortgagee, who knowingly allows the building, room, space, or enclosure to be fortified to suppress law enforcement entry in order to further the sale of any amount of cocaine, heroin, or phencyclidine and who obtains excessive profit from the use of the building, room, space, or enclosure shall be punished by imprisonment in the state prison for two, three, or four years.”