While traveling on West Chester Pike in Newtown Township, Delaware County, appellee Robert Shenkin’s vehicle was clocked at 66 miles per hour by an officer of the Newtown Township Police Department using a speed timing device known as the Excessive Speed Preventer (“E.S. P.”) Model TK 100. 1 The posted speed limit at the relevant location on West Chester Pike is 40 miles per hour. Appel-lee was issued a citation for exceeding the posted speed limit in violation of section 3362 of the Vehicle Code, 75 Pa.C.S. § 3362.
Appellee was found guilty of the offense of speeding in a summary trial before a district justice. He filed a timely appeal from the judgment of the District Court. At the non-jury trial de novo in the Court of Common Pleas of Delaware County, Shenkin demurred to the Commonwealth’s evidence. His demurrer raised, inter alia, the issue of whether section 6109(b) of the Vehicle Code, 75 Pa.C.S. § 6109(b), required Newtown Township to enact an ordinance authorizing its police department to use the E.S.P. timing device. Appellee’s demurrer was overruled and he presented a defense in which he continued to attack the *520 legal authority of the Newtown Township police to use the E.S.P. device. 2
The trial court then found appellee guilty of speeding. Appellee filed timely post-verdict motions for a new trial and in arrest of judgment. In addition to boilerplate challenges to the weight and sufficiency of the evidence, the post-verdict motions renewed appellee’s contention that Newtown Township was without legal authority to enforce speed limits using the E.S.P. device, because no local ordinance was enacted authorizing such actions. On August 17, 1982, the trial court granted appellee’s motion in arrest of judgment by an order which reads as follows: “AND NOW, to wit, this 17th day of August, 1982 having heard testimony, reviewed briefs submitted by both parties, it is hereby ordered that Defendant’s post-verdict motion is granted, the appeal is sustained, and the Defendant is found not guilty.” The Commonwealth brings the instant appeal from this order. For the reasons stated below, we reverse and remand.
We begin our inquiry with a consideration of whether this order is appealable by the Commonwealth. Although neither party briefed or argued the issue, we must address the appealability of the order sua sponte, since it is a question going to the jurisdiction of the appellate court. This Court may not act where it is without jurisdiction, even if the parties consent.
See, e.g., Balter v. Balter,
In the instant case, it is evident from the opinion filed by the trial court that its decision to grant the motion in arrest of judgment was based on the resolution of a question of law, namely whether Newtown Township’s use of the E.S.P. timing device was improper because of the lack of an authorizing ordinance. However, the order entered
*521
by the trial court, in addition to granting “Defendant’s post-verdict motion,” also states that “the Defendant is found
not guilty
” (emphasis added). We are thus faced with two competing principles in deciding whether the Commonwealth may appeal under these circumstances. The first is the general rule that the Commonwealth may appeal an order arresting judgment where a pure question of law is involved.
Commonwealth v. Glendening,
The “judgments of not guilty” in both
Haines
and
Burton
were simply verdicts entered by the trial judge in non-jury trials. Hence, their holdings rest on the fundamental principle that the Commonwealth may not appeal from an acquittal of the defendant, a rule grounded on the Double Jeopardy Clause of the Fifth Amendment.
See Commonwealth v. Maurizio,
We hold that the trial court’s incorrect use of the words “not guilty” does not convert its ruling on appellee’s motion in arrest of judgment into an unappealable acquittal. This Court sitting en banc, following relevant United States Supreme Court decisions, has held that this is a question of substance, not one of form or of technical interpretation of words. In
Commonwealth v. Smalis,
Examining the trial court’s ruling in the instant case in light of Smalis, and reading the trial court’s order in the context of appellee’s motions and the court’s opinion, as Martin Linen allows us, it becomes clear that the sole basis for the arrest of judgment was a legal determination. Therefore we find that the order is not an “acquittal” for double jeopardy purposes, despite its incorrect inclusion of the words “not guilty.”
Applying the
Scott
test, we further find that the order is appealable, because reversal would not require a retrial. Since the court initially entered a verdict of guilty and reversed itself on post-verdict motions, the result of reversal of the order from which the appeal was taken will simply be the reinstatement of the original guilty verdict. No retrial or any other . “ ‘further proceedings ... devoted to the resolution of factual issues going to the elements of the offense charged,’ ”
Smalis,
In this latter respect, the instant case is clearly distinguishable from Haines and Burton. In Haines and Burton the ruling appealed from was the original verdict of the trial judge, so a new trial would be required upon reversal.
These distinctions are by no means novel. In the
Haines
opinion itself, our Supreme Court indicated that it did not intend appeals from arrests of judgment to come within the
*523
ambit of its holding. The court cited
Commonwealth v. Obenreder,
See also Commonwealth v. Davis,
The principles of
Martin Linen and Scott
are also not new to Pennsylvania jurisprudence. In
Commonwealth v. Wimberly,
*524
We recognize that our holding in
Commonwealth v. Thinnes,
Having established that the Commonwealth’s appeal is properly before this Court, we turn to the merits. Appellee argued, and the trial court held, that the Commonwealth’s evidence of speed must be excluded because there was no local ordinance authorizing the use of the E.S.P. Model TK 100 timing device by the Newtown Township police. We disagree. In the recent decision of this Court in
Commonwealth v. DePasquale,
Appellee further argues that the trial court’s decision should be affirmed even if the police’s use of the E.S.P. device itself was properly authorized, because there were no traffic signs warning of the use of this particular enforcement device. This contention is also disposed of by
DePasquale.
We held that the requirement of 75 Pa.C.S. § 6109(c) that “official traffic control devices” be posted requires only signs informing motorists of the speed limit or other regulation itself, not of the specific means of their enforcement.
See DePasquale,
Finally, appellee contends that the evidence of speed must be excluded because the Commonwealth failed to prove the existence of an agreement between the New-town Township police and the Pennsylvania State Police pursuant to 75 Pa.C.S. § 6109(a)(ll) authorizing the New-town Township police to enforce speed limits on West Chester Pike, a divided highway. We agree with the Commonwealth that this issue is properly raised as an affirmative defense, and that appellee has therefore waived it because he presented no evidence on the question at trial. The existence of such an agreement is not an element of the offense of speeding as it is defined in 75 Pa.C.A. § 3362. Although the Commonwealth undeniably has the burden of proving every element of the offense charged beyond a reasonable doubt,
Commonwealth v. Bishop,
We therefore reverse the order granting appellee’s motion in arrest of judgment. In its opinion, the trial court stated that because it granted the motion in arrest of judgment, it did not consider appellee’s other requests for post-verdict relief. These requests included a motion for a new trial. Appellee is entitled to have the trial court consider his motion for a new trial on remand following our reversal of the order granting the arrest of judgment.
Commonwealth v. Meadows,
Order reversed and case remanded for consideration of appellee’s outstanding post-verdict motions for a new trial, and further proceedings consistent with this opinion. Jurisdiction is. relinquished.
Notes
. For a complete description of the E.S.P. Model TK 100, see our opinion in
Commonwealth v. DePasquale,
. Appellee also presented evidence on the factual issues. He testified that another vehicle, which was overtaking him in the adjacent lane, passed over the sensors of the E.S.P. device simultaneously with his vehicle. The trial court indicated that it resolved this factual issue against appellee. See N.T. 4/12/82 at 35.
. The right of the Commonwealth to appeal orders sustaining defense demurrers has been substantially modified by
Commonwealth v. Smalis,
