Why should Fourth Amendment protections be lessened to prevent the destruction of evidence?

Why would the destruction of evidence, or even the suspicion of destruction of evidence, constitute exigent circumstances that creates an exception to the Fourth Amendment? Yes, I know this is nothing new, but I have been thinking about this since Kentucky v. King.

I understand why threats to an officer’s safety, or the safety of other’s constitutes exigent circumstances that supports vitiating Fourth Amendment rights (this fits into my Constitutionality of Social Cost framework).

But how does the destruction of evidence fit into that calculus? Perhaps if the destruction of evidence (by burning maybe?) poses a threat to others that fits, but what difference does it make if a suspect flushes evidence down the toilet–a plumber may be upset, but no one else is at risk of being harmed.

Now, the obvious answer is that it makes it more difficult for the state to prosecute the crime, and put the bad guy behind bars. But, so what? What “right” does the government have to evidence. I suppose destruction of evidence could be a crime, but my question, more broadly, is why a constitutional right is limited in these cases.

The government has no right to prosecute someone. The state does not have rights, it has power. Only people have rights. That power is constrained by the rights guaranteed by the Constitution. Exceptions to those powers based on those rights are just that, exceptions.

So why is the need to prosecute someone sufficient enough to weaken Fourth Amendment protections, and unreasonably search or seize property on belief of destruction of evidence?

Update: Justice Scalia’s concurring opinion in  Thornton v. US is somewhat elucidating here, focusing on the government’s “interest” in gathering evidence incident to a lawful arrest. Scalia further notes that the fact that there was a prior lawful arrest “distinguishes the arrestee from society at large.” In other words, he has taken an affirmative act which exemplified a propensity for danger. Even if the interest here is appropriate for an arrestee, I would distinguish this from the exigent circumstances doctrine at issue in Kentucky v. King, wherein a person has done nothing to show this dangerousness, and the police simply suspect the destruction of evidence. I sense another article germinating applying the Constitutionality of Social Cost to broader 4th amendment issues.

Here is the important part of the opinion:

If Belton searches are justifiable, it is not because the arrestee might grab a weapon or evidentiary item from his car, but simply because the car might contain evidence relevant to the crime for which he was arrested. This more general sort of evidence-gathering search is not without antecedent. For example, in United States v. Rabinowitz,339 U.S. 56 (1950), we upheld a search of the suspect’s place of business after he was arrested there. We did not restrict the officers’ search authority to “the area into which [the] arrestee might reach in order to grab a weapon or evidentiary ite[m],” Chimel, 395 U.S., at 763, and we did not justify the search as a means to prevent concealment or destruction of evidence.1Rather, we relied on a more general interest in gathering evidence relevant to the crime for which the suspect had been arrested. See 339 U.S., at 60—64; see also Harris v. United States,331 U.S. 145, 151—152 (1947); Marron v. United States,275 U.S. 192, 199 (1927); Agnello v. United States,269 U.S. 20, 30 (1925); cf. Weeks v. United States,232 U.S. 383, 392 (1914).

Numerous earlier authorities support this approach, referring to the general interest in gathering evidence related to the crime of arrest with no mention of the more specific interest in preventing its concealment or destruction. See United States v. Wilson, 163 F. 338, 340, 343 (CC SDNY 1908); Smith v. Jerome, 47 Misc. 22, 23—24, 93 N. Y. S. 202, 202—203 (1905);Thornton v. State, 117 Wis. 338, 346—347, 93 N. W. 1107, 1110 (1903); Ex parte Hurn, 92 Ala. 102, 112, 9 So. 515, 519—520 (1891); Thatcher v. Weeks, 79 Me. 547, 548—549, 11 A. 599, 599—600 (1887); 1 F. Wharton, Criminal Procedure §97, pp. 136—137 (J. Kerr 10th ed. 1918); 1 J. Bishop, Criminal Procedure §211, p. 127 (2d ed. 1872); cf. Spalding v. Preston, 21 Vt. 9, 15 (1848) (seizure authority); Queen v. Frost, 9 Car. & P. 129, 131—134 (1839) (same); King v.Kinsey, 7 Car. & P. 447 (1836) (same); King v. O’Donnell, 7 Car. & P. 138 (1835) (same); Kingv. Barnett, 3 Car. & P. 600, 601 (1829) (same). Bishop’s 1872 articulation is typical:

“The officer who arrests a man on a criminal charge should consider the nature of the charge; and, if he finds about the prisoner’s person, or otherwise in his possession, either goods or moneys which there is reason to believe are connected with the supposed crime as its fruits, or as the instruments with which it was committed, or as directly furnishing evidence relating to the transaction, he may take the same, and hold them to be disposed of as the court may direct.” Bishop, supra, §211, at 127.

Only in the years leading up to Chimel did we start consistently referring to the narrower interest in frustrating concealment or destruction of evidence. See Sibron v. New York,392 U.S. 40, 67 (1968); Preston v. United States,376 U.S. 364, 367 (1964).

There is nothing irrational about broader police authority to search for evidence when and where the perpetrator of a crime is lawfully arrested. The fact of prior lawful arrest distinguishes the arrestee from society at large, and distinguishes a search for evidence of hiscrime from general rummaging. Moreover, it is not illogical to assume that evidence of a crime is most likely to be found where the suspect was apprehended.

Nevertheless, Chimel’s narrower focus on concealment or destruction of evidence also has historical support. See Holker v. Hennessey, 141 Mo. 527, 539—540, 42 S. W. 1090, 1093 (1897); Dillon v. O’Brien, 16 Cox C. C. 245, 250 (Ex. Div. Ire. 1887); Reifsnyder v. Lee, 44 Iowa 101, 103 (1876); S. Welch, Essay on the Office of Constable 17 (1758).2 And some of the authorities supporting the broader rule address only searches of the arrestee’s person, as to which Chimel’s limitation might fairly be implicit. Moreover, carried to its logical end, the broader rule is hard to reconcile with the influential case of Entick v. Carrington, 19 How. St. Tr. 1029, 1031, 1063—1074 (C. P. 1765) (disapproving search of plaintiff’s private papers under general warrant, despite arrest). But cf. Dillon, supra, at 250—251 (distinguishingEntick); Warden, Md. Penitentiary v. Hayden,387 U.S. 294, 303—304 (1967).

In short, both Rabinowitz and Chimel are plausible accounts of what the Constitution requires, and neither is so persuasive as to justify departing from settled law. But if we are going to continue to allow Belton searches on stare decisis grounds, we should at least be honest about why we are doing so. Belton cannot reasonably be explained as a mere application of Chimel. Rather, it is a return to the broader sort of search incident to arrest that we allowed before Chimel–limited, of course, to searches of motor vehicles, a category of “effects” which give rise to a reduced expectation of privacy, see Wyoming v. Houghton, 526 U.S. 295, 303 (1999), and heightened law enforcement needs, see id., at 304; Rabinowitz, 339 U.S., at 73 (Frankfurter, J., dissenting).