A jury found Phillip Coleman guilty of four counts of being a felon in possession of a firearm, see 18 U.S.C. § 922(g)(1) (as well as one count of unlawful possession of an unregistered firearm, see 26 U.S.C. § 5861(d); a conviction not in issue here). Coleman attacks the gun convictions on three grounds: 1) that the four felon-in-possession counts were misjoined (or, in the alternative, erroneously not severed); 2) that for one of those counts the government’s evidence was insufficient to establish that the gun traveled in interstate commerce — a necessary element of the offense; and 3) that for the same count the underlying search and seizure was unreasonable. We are not persuaded by any of these submissions and accordingly affirm all of the convictions.
I.
The four possession counts were premised upon four separate incidents occurring on April 18, 1990, January 14, 1992, May 23, 1992, and June 2, 1992. While the first two are essentially unconnected with each other and with the latter two, there is slightly more than mere temporal proximity linking the events of May 23 and June 2. On May 23, Milwaukee police officers observed Coleman pointing a small gun at another man and gave chase on foot. After catching up with Coleman and recovering a small gun from underneath a dumpster located along the route Coleman took, the officers ran a warrant cheek on Coleman and found none outstanding. Coleman told the officers that he was chasing three men who had tried to break into his house, and because of a mixup among the officers, Coleman was released. Five days later one of the officers telephoned Coleman’s parole officer, Susan Dybul, and told her that Coleman was seen chasing another man with a handgun. (Coleman was on parole after serving prison time for weapon possession, burglary and attempted murder; possession of firearms violated the conditions of his parole.) The officer also told Dybul that he was planning to refer the case to federal authorities. Later that day, Coleman called Dybul and reported that he was arrested and released the previous day in a separate incident — driving with a revoked license. Planning to take him into custody because of the weapon possession report, Dybul told Coleman to report to her office on June 2 at 9:30 a.m. Meanwhile, a federal agent, who had been contacted by .the Milwaukee police, called Dybul and arranged to arrest Coleman on federal charges when Coleman appeared at Dybul’s office.
*129 On June 2, before Coleman was due to arrive, Dybul received a call from Cheryl Williams who claimed that Coleman had stolen her pistol from her purse six days earlier because she owed him seventy dollars for cocaine he had provided. In the conversation, Williams identified herself, provided an address and two telephone numbers, described the gun and confirmed that it was bought and registered in her name. Dybul told Williams to file a police report, which she did. Because of Williams’ call, Dybul then met with her supervisor, and they discussed conducting a search of Coleman’s home. (Under applicable procedures, Dybul and her supervisor would need the approval of their assistant regional chief to conduct a home search.) A short time later, the federal agents arrived as arranged, and Dybul informed them about Williams’ call and the parole search which was being planned as a result. She asked them, and they agreed, to assist in the search by providing backup. In the meantime, Dybul’s supervisor received permission to carry out the search, and the Milwaukee police phoned Dybul to inform her that Williams had filed a report regarding her missing gun. When Coleman arrived at Dybul’s office at 9:30, the federal authorities arrested him. Soon afterwards, Dybul, her supervisor and two federal agents drove to Coleman’s residence and entered the home using a key that was seized from Coleman. After the federal agents conducted a brief protective sweep, Dybul and her supervisor searched the house. On the second floor, Dybul found a sawed-off shotgun which was to become the subject of Count III of the indictment.
II.
A.
Coleman argues that the shotgun should have been suppressed as a fruit of an illegal search. Acknowledging that Wisconsin’s procedure for warrantless searches of probationers’ homes is constitutional,
1
see Griffin v. Wisconsin,
These arguments we can reject in short order. First of all, while we agree that federal law enforcement officers (or the police in general) cannot utilize state probation officials to carry out warrantless searches on their behalf which they as federal agents, acting alone, could not execute without a judicial warrant,
see, e.g., Shea v. Smith,
Coleman’s alternative claim that Dybul did not have “reasonable grounds” to believe his residence contained contraband as required under Wisconsin’s probation search procedure is also without merit. In
Griffin,
the Supreme Court found that the Wisconsin procedure, with its definition of “reasonable grounds,” comports with the Fourth Amendment’s reasonableness requirement and thus a search carried out pursuant to it is valid. Accordingly, if Dybul’s search of Coleman’s home complied with that scheme, the search passes constitutional muster.
2
“Reasonable grounds” denotes a degree of certainty less than that of probable cause,
see Wisconsin v. Griffin,
B.
Coleman argues that his conviction for possession of the shotgun found by Dybul should be reversed anyway because evidence sufficient to prove beyond a reasonable doubt that the weapon moved in interstate commerce was not presented to the jury. If true, the government concedes, such an oversight would constitute a defect mandating reversal.
See United States v. Buggs,
STEVENS SAVAGE ARMS CORPORATION
CHICOPEE FALLS, MASS U.S.A.
In closing argument, the government explicitly invited the jury to look at the markings on the guns for proof of interstate commerce nexus, while Coleman, despite the testimony of the ATF expert, urged the jury to consider that the markings may only represent the home office of the manufacturing corporation and not the actual place of manufacture. The jury was entitled to inspect the weapon for themselves and draw the conclusion, based on the ATF agent’s testimony, that the markings were dispositive of out-of-state production. The record is certainly not “barren of any evidence, regardless of weight, from which the trier of fact could find [this element] beyond a reasonable doubt.”
United States v. Kaufmann,
C.
Coleman contends that the four separate weapons possession charges were misjoined or at least should have been severed. Joinder of offenses is proper when, on among other occasions, the offenses “are of the same or similar character.” Fed. R.Crim.P. 8(a).
5
Although Rule 8(a) speaks to nothing more than the similarity between joined counts, this court, following the lead of the eighth circuit, has opined that this kind of joinder is permitted if “the counts refer to the same type of offenses occurring over a relatively short period of time, and the evidence as to each count overlaps.”
United States v. Koen,
The short-period-of-time/evidence-overlap formula reflects a concern that the liberal joinder rule not result in the unchecked bundling of offenses. It recognizes that the value of joining offenses in a particular case depends upon the extent to which real efficiencies can be realized with minimal concomitant prejudice to the conduct of a fair trial. Judicial economy and convenience are the chief virtues of joint trials — i.e. joinder often avoids expensive and duplicative multiple
trials
— see
Archer,
But is it precisely the joinder
rule
(or
this
joinder rule) that should be informed by such a necessarily discretionary estimate of the evidence? Interestingly, the eighth circuit’s formulation in which time separation and evi-dentiary overlap between offenses are prominent may have originated as a guide not to joinder of offenses of “same or similar character” but to joinder of offenses that form a common plan or scheme,
see United States v. McKuin,
pare the offenses charged for categorical, not evidentiary, similarities.
9
Further, the similarity of character of different offenses does not significantly depend on their separation in time. Two armored car robberies committed months apart are offenses of same or similar character; possessing five kilograms of cocaine and defrauding a bank, even if they occur on the same day, are not. Simply put, if offenses are of like class, although not connected temporally or evidentially, the requisites of proper joinder should be satisfied so far as Rule 8(a) is concerned.
10
This was the thrust of earlier cases applying the Rule,
see, e.g., United States v. Quinn,
This approach is most consistent with the respective roles of Rule 8 and Rule 14. Rule 8 joinder is based solely on the face of the indictment and is accordingly a question of law, subject to plenary appellate review.
See United States v. Shue,
Because Rule 8 does represent a strong preference, in language and policy, for broadly construing the propriety of joinder as an initial matter,
see Archer,
Here, joinder under Rule 8(a) was appropriate because Coleman was charged with four counts of possession of a firearm, identical 922(g)(1) offenses which could only vary in time and location but not in their essential elements. Furthermore, we cannot conclude under the circumstances
*135
of this case, considering especially the amount and nature of the evidence and the nature of the joined counts, that the denial of Coleman’s severance motion was an abuse of the district court’s discretion. “[T]he evidence as to each was short and simple; there was no reasonable ground for thinking that the jury could not keep separate what was relevant to each.”
Lotsch,
III.
Because we conclude that the district court did not err by allowing the charges to be tried together, by denying the suppression motion or by sustaining the jury’s verdict, all the challenged convictions are affirmed.
Notes
. Wisconsin's probation regulations were imposed upon Coleman as a condition of parole.
. And if the search and seizure were constitutional (and otherwise in accord with federal law), the evidentiary proceeds can be used in a federal prosecution although garnered by state officials.
See United States v. Singer,
. The Wisconsin procedure instructs probation agents to consider:
(a) observations of staff members;
(b) information provided by informants;
(c) reliability of the information, with attention given to whether it is detailed and consistent and whether it is corroborated;
(d) reliability of the informant, with attention given to whether the informant has supplied reliable information in the past and whether the informant has reason to supply inaccurate information;
(e) activity of the client that relates to whether the client might possess contraband;
(f) information provided by the client that is relevant to whether the client possesses contraband;
(g) experience of a staff member with that client or in a similar circumstance;
(h) prior seizures of contraband from the client; and
(i) need to verify compliance with rules of supervision and state and federal law.
See Wisconsin Administrative Code DOC § 328.-21(6).
. This was the exchange on redirect examination:
Q. And you were not able to determine if any manufacturer in the State of Wisconsin manufactured these four weapons?
A. No, I'm very familiar with these. I deal with these virtually every day. Especially these weapons. This is the most common Saturday night special in the state. Our office has got hundreds of these.
As the three other weapons were handguns (two small caliber pistols and a derringer), it is unclear whether the agent, by his reference to Saturday night specials (a term for small, inexpensive handguns), was also contemplating the Savage Arms shotgun when framing his response.
. Rule 8(a) also permits joinder when offenses are “based on the same act or transaction or on two or more acts or transactions connected together or constituting part of a common scheme or plan." It is undisputed that this case does not involve either of these brands of joinder.
. The magistrate below acknowledged that this longer interval, approaching two years, "may perhaps be reaching the outer edge of a 'relatively short period of time,' ” but upheld joinder of
*132
all counts because of our general instruction to construe Rule 8 broadly to allow joinder.
See United States v. Archer,
. There is at least a slight link between the May 23 and June 2 incidents — Dybul originally summoned Coleman for the office visit on June 2 because of a report of his May 23 gun possession which, in part, constituted grounds for the parole search of his home on June 2. However, the government has not argued nor is it obvious that this connection between the incidents would have been relevant at trial.
. Note, however, that these concerns in fact may be greatly diminished at joint trials. Judge Learned Hand explained:
There is indeed always a danger when several crimes are tried together, that the jury may use the evidence cumulatively; that is, that, although so much as would be admissible upon any one of the charges might not have persuaded them of the accused's guilt, the sum of it will convince them as to all. This possibility violates the doctrine that only direct evidence of the transaction charged will ordinarily be accepted, and that the accused is not to be convicted because of his criminal disposition. Yet in the ordinary affairs of life such a disposition is a convincing factor, and its exclusion is rather because the issue is practically un *133 manageable than because it is not rationally relevant. When the accused’s conduct on several separate occasions can properly be examined in detail, the objection disappears, and the only consideration is whether the trial as a whole may not become too confused for the jury.
United States
v.
Lotsch,
. Contrast this language with the language delineating the other types of offense joinder recognized in Rule 8(a) and the case-specific reference used: "Two or more offenses may be charged in the same indictment ... if the offenses charged ... are based on the same act or transaction or on two or more acts or transactions connected together or constituting parts of a common scheme or plan” (emphasis added).
. The offenses need not be of identical statutory origin in order to be
similar,
but their correspondence in type is obviously central to their proper joinder on this ground.
See United States v. Werner,
We do not mean to suggest that when offenses are joined for their similarity, proximity in time is irrelevant; it is just so rarely probative of sameness of offenses — and so infrequently dis-positive of similarity — that to incorporate time separation as part of a test under this portion of Rule 8(a) vastly overstates its typical degree of relevance to the joinder inquiry.
. Rule 14 reads:
If it appears that a defendant or the government is prejudiced by a joinder of offenses or of defendants in an indictment or information or by such joinder for trial together, the court may order an election or separate trials of counts, grant a severance of defendants or provide whatever other relief justice requires ....
. Indeed, as the government points out, a far greater potential for inflammatory or inferential prejudice inhered in the nature of the predicate felony for the 922(g)(1) counts — attempted murder — whose mention indisputably was an appropriate component of the trial, than in the respective gun possession counts themselves.
