I. Introduction
In this appeal we construe the term “law enforcement agency” as it is used in section 16 — 10—103(l)(k), C.R.S. (2005), which requires a trial court in a criminal case to grant a challenge for cause to a prospective juror who is a compensated employee of a public law enforcement agency.1 We review the court of appeals’ decision in People v. Ma, 104 P.3d 273 (Colo.App.2004), which held that the trial court properly denied Ma’s challenge for cause to a prospective juror who is an Army military police reservist and affirmed Ma’s criminal convictions for criminal mischief and menacing. It reasoned that the Army Military Police Corps is a subdivision of the Department of Defense, which is not a law enforcement agency.
We construe the term “law enforcement agency” to mean a police-like division or subdivision of government that has the authority to investigate crimes and to arrest, to prosecute, or to detain suspected criminals. The common definition of the word “agency” is a division or subdivision of government. The common understanding of the phrase “law enforcement” is the detection and punishment of criminal violations of the law by the police or other police-like agencies. The Army Military Police Corps is a subdivision of government that detects and punishes criminal violations of the law by performing police-like functions such as arresting suspected criminals, investigating crimes, and detaining prisoners. Hence, we hold that the Army Military Police Corps is a law enforcement agency for the purpose of section 16-10 — 103(l)(k).
Under the facts presented here, we hold that the trial court should have granted Ma’s challenge for cause. For these reasons, we reverse the judgment of the court of appeals and return this case to that court with instructions to remand it to the trial court for a new trial.
II.Facts and Proceedings Below
During jury selection, the trial court asked whether any of the prospective jurors was an employee of a law enforcement agency. One prospective juror told the trial court that he serves as a platoon leader in the Army Military Police Reserves. He explained that he works one weekend a month and participates in military police combat and site security missions.
The trial court then called counsel to the bench and stated, “Just when you think the *208phrase ‘law enforcement agency’ is clear, the world intrudes on your language.” The trial court then asked if either party wanted to challenge the prospective juror for cause. In response to this question, the prosecutor said, “I don’t at this point.” And, defense counsel replied, “I don’t.”
Later, the trial court asked the prospective juror whether he had ever testified in court. The prospective juror explained that he had testified as a military police officer in cases involving petty theft, drunk and disorderly conduct, and domestic disputes. When it was the defense’s turn to question the prospective juror, defense counsel clarified that the prospective juror was a military police officer who had testified in a police capacity in criminal cases like this one. Defense counsel then challenged the prospective juror for cause under section 16 — 10—103(l)(k).
The trial court denied the challenge, ruling that defense counsel had waived Ma’s right to make such a challenge when he first declined the opportunity to do so.2 As a result of that ruling, defense counsel used one of Ma’s peremptory challenges to excuse the prospective juror and ultimately exercised all of Ma’s peremptory challenges. The jury found Ma guilty of criminal mischief and menacing.
On appeal, the court of appeals held that the trial court properly denied Ma’s challenge for cause. Ma, 104 P.3d at 277-78. But instead of concluding, as the trial court had, that defense counsel waived Ma’s right to make the challenge, the court of appeals concluded that such a challenge was invalid. Id. It reasoned that the prospective juror was not within the reach of section 16-10-103(l)(k) because the Army Military Police Corps is not a law enforcement agency, but rather is a subdivision of the Department of Defense, which is not a law enforcement agency. Id.
We granted Ma’s petition for certiorari on the question of whether the trial court should have granted Ma’s challenge for cause in order to address the particular issue of what the term “law enforcement agency” means as it is used in section 16 — 10—103(l)(k).3
*209III. Analysis
A. Waiver of the Challenge for Cause
As a threshold matter, we address whether defense counsel waived Ma’s right to challenge the prospective juror for cause by declining an initial opportunity to do so.
Ma maintains that defense counsel was uninformed and unaware that his initial refusal to challenge the prospective juror would preclude him from making such a challenge after further questioning. In contrast, the People argue that defense counsel waived Ma’s right to make the challenge by failing to pursue the matter when the grounds for making the challenge were first raised.
A challenge for cause is waived if counsel fails to use reasonable diligence during jury selection to determine whether the grounds for such a challenge exist. People v. Lewis, 180 Colo. 423, 428, 506 P.2d 125, 127 (1973). The test for reasonable diligence is whether counsel took the opportunity to adequately question a prospective juror. Brown v. People, 20 Colo. 161, 165, 36 P. 1040, 1042 (1894).
Although the determination that a waiver was valid is largely within the discretion of the trial court, see People ex rel. Peters v. District Court, 951 P.2d 926, 931 (Colo.1998), the record in this ease lacks the information necessary for us to find a waiver.
After the prospective juror stated that he was an Army military police reservist, the trial court commented that the term “law enforcement agency” is unclear. It then asked whether either party wanted to make a challenge for cause. It did not ask if either party wanted to question the potential juror further. Nor did it state that this was the parties’ only chance to make such a challenge.
In response to the trial court’s question, the prosecutor said that he did not want to make a challenge “at this time.” Defense counsel replied that he did not want to make a challenge either. Eventually, when it was the defense’s turn to question the prospective juror, defense counsel asked him about his job as an Army military police reservist. It was at that time that defense counsel challenged the prospective juror for cause.
It is clear that defense counsel initially declined the opportunity to challenge the prospective juror for cause. It is unclear, however, that defense counsel’s decision constituted a waiver. When the grounds for making the challenge were first raised, defense counsel did not ask the prospective juror any questions. But, when it was defense counsel’s turn to question the prospective juror, defense counsel raised the issue again.
Because defense counsel eventually questioned the prospective juror regarding the grounds for making the challenge, we cannot conclude that defense counsel failed to use reasonable diligence unless the record is clear that defense counsel was aware that his initial opportunity to challenge the prospective juror would be his only opportunity to do so. The record is unclear on this point. Hence, we hold that the record is insufficient to support the conclusion that defense counsel waived Ma’s right to challenge the prospective juror for cause under section 16 — 10— 103(l)(k).
B. Merits of the Challenge for Cause
We next address the issue of whether the trial court should have granted Ma’s challenge for cause to a prospective juror who is an Army military police reservist.
Ma argues that the Army Military Police Corps is a law enforcement agency because it is the law enforcement arm of the Army, just as a city’s police department is the law enforcement arm of that city. The People, on the other hand, contend that the Army Military Police Corps is not a law enforcement agency because it is a subdivision of the Department of Defense, which is not a law enforcement agency.
Before we begin our analysis of this issue, we note that the rationale underlying a challenge for cause to a compensated employee *210of a public law enforcement agency is to ensure that the jury in a criminal ease remains impartial in both fact and appearance. People in the Interest of R.A.D., 196 Colo. 430, 432, 586 P.2d 46, 47 (1978); see Tate v. People, 125 Colo. 527, 538-540, 247 P.2d 665, 670-71 (1952). The concern is that one who is employed by a law enforcement agency will favor, or will be perceived to favor, the prosecution side of a criminal ease. People in the Interest of R.A.D., 196 Colo. at 432, 586 P.2d at 47.
Because a criminal defendant has the constitutional right to a fair trial by an impartial jury, see U.S. Const, amend. VI; Colo. Const, art. II, § 16, a trial court in a criminal case must grant all valid challenges for cause, see § 16-10-103; Carrillo v. People, 974 P.2d 478, 486-87 (Colo.1999). Even so, a trial court’s failure to grant a valid challenge for cause requires retrial only if the defendant used a peremptory challenge to excuse the prospective juror and then exercised all available peremptory challenges.4 Carrillo, 974 P.2d at 486-87.
1. The Term “Law Enforcement Agency”
We now begin our analysis of this issue, which requires us to construe the definition of the term “law enforcement agency” as it is used in section 16 — 10—103(l)(k). Words and phrases are to be construed according to their common usage unless they have acquired a technical or particular meaning, whether by legislative definition or otherwise. § 2-4-101, C.R.S. (2004); Binkley v. People, 716 P.2d 1111, 1113 (Colo.1986).
The term “law enforcement agency” is not defined by section 16-10-103 or by any of the other statutes that govern jury selection and composition. See §§ 16-10-101 to 110, C.R.S. (2005). Therefore, we construe the term’s meaning according to its common usage.
The word “agency” is defined as a “division of government.” American Heritage Dictionary of the English Language 32, (4th ed.2000).
The phrase “law enforcement” is defined as “the detection and punishment of violations of the law.” Black’s Law Dictionary 891 (7th ed.1999). Detecting and punishing violations of law is commonly understood to be the job of the police or other police-like agencies. See American Heritage Dictionary of the English Language, supra at 1358 (defining the word “police” as “the governmental department ... established to maintain order, enforce the law, and prevent and detect crime”). Police officers are responsible for enforcing criminal laws. They do this by investigating crimes, and arresting, detaining, and assisting in the prosecution of suspected criminals. See, e.g., Denver Police Dep’t. Denver Police Dep’t Operations Manual (2004). Therefore, the common understanding of the phrase “law enforcement” conjures up images of police officers carrying out typical police functions in order to enforce criminal laws.
In the broadest sense, the phrase “law enforcement” means not only the enforcement of criminal laws but also the enforcement of civil regulations. Black’s Law Dictionary, supra at 891. However, when a word can be defined in either a broad or a narrow sense, the definition that will best effectuate the General Assembly’s intent should be applied. Fifteenth St. Inv. Co. v. People, 102 Colo. 571, 581, 81 P.2d 764, 769 (1938).
The broad meaning of the phrase “law enforcement” includes the enforcement of both criminal laws and civil regulations. But, to apply this meaning would enlarge the pool of dismissible jurors to a size that was not contemplated by the General Assembly. See People v. Simon, 100 P.3d 487, 491 (Colo.App.2004) (observing that the General Assembly did not intend for all employees of the EPA to be disqualified under the statute). The narrow meaning of the phrase “law enforcement” is limited to the enforcement of criminal laws. To apply this mean*211ing would keep the pool of dismissible jurors to an appropriate size and would also achieve the General Assembly’s goal of maintaining actual and apparent jury impartiality. See People in Interest of R.A.D., 196 Colo. at 432, 586 P.2d at 47.
When we construe a statute, our goal is to ascertain and to give effect to the General Assembly’s intent. People v. Guenther, 740 P.2d 971, 975 (Colo.1987). Thus, we construe the phrase “law enforcement” to mean the enforcement of criminal laws by the police or other police-like agencies.
In addition to reflecting the phrase’s common definition and the General Assembly’s intent, our construction of the phrase “law enforcement” finds support throughout Colorado statutory and case law. The statutes that define the term “law enforcement agency” also identify several types of law enforcement agencies, including: any police department, sheriffs department, or district attorney’s office; the office of the state attorney general; the Colorado bureau of investigations; and the Colorado state patrol. §§ 8^7-203.3(2), 8-72-111(2), 24-50-127(2)(b), 26-l-114(3)(a)(III)(B), C.R.S. (2005) (statutes about state employee benefits and protections); § 42-5-201(6), C.R.S. (2005) (a statute about traffic regulations). Notably, each of these agencies enforces criminal laws, thus reinforcing the notion that the phrase “law enforcement” does not imply the enforcement of civil regulations.
In a number of cases, the court of appeals has held that agencies responsible for enforcing civil regulations are not law enforcement agencies for the purpose of section 16-10-103(l)(k). See, e.g., People v. Zurenko, 833 P.2d 794, 796 (Colo.App.1991) (Department of Social Services and Equal Employment Opportunity Commission); People v. Topping, 764 P.2d 369, 370 (Colo.App.1988) (State Department of Administration), aff'd on other grounds, 793 P.2d 1168 (Colo.1990); People v. Urrutia, 893 P.2d 1338, 1346 (Colo.App.1994) (Department of Defense); Simon, 100 P.3d at 491 (Environmental Protection Agency); cf. People v. Scott, 41 Colo.App. 66, 583 P.2d 939, 941 (1978) (holding that the Department of Corrections is a law enforcement agency because some of the agency’s personnel have the power to arrest); People v. Maes, 43 Colo.App. 365, 609 P.2d 1105, 1107 (1979) (holding that a challenge for cause to a mechanic in the Denver Police Department’s garage should have been granted). Through these cases, the court of appeals has implicitly construed the phrase “law enforcement,” contained in section 16 — 10—10S(l)(k), to connote only the enforcement of criminal laws.
Combining the common meanings of the phrase “law enforcement” and the word “agency,” we reason that the term “law enforcement agency” means a division of government that detects and punishes criminal violations of the law by performing police-like duties such as investigating crimes and arresting, prosecuting, or detaining suspected criminals. Put in a less cumbersome way, a law enforcement agency is a police-like division of government that has the authority to investigate crimes and to arrest, to prosecute, or to detain suspected criminals.
2. The Army Military Police Corps
Having construed what the term “law enforcement agency” means as it is used in section 16 — 10—103(l)(k), we turn to the specifics of this case and consider two questions: first, whether the Army Military Police Corps is an agency; and second, if so, whether it is a law enforcement agency.
As to the first question, the court of appeals determined that the Army Military Police Corps is not an agency in and of itself. Ma, 104 P.3d at 277-78. Because of this determination, the court of appeals did not analyze whether the Army Military Police Corps is a law enforcement agency, but instead analyzed whether the Department of Defense, which oversees the Army, is one. Id.
Contrary to the court of appeals, we see no reason why the Army Military Police Corps should not be considered an agency in and of itself. It is true that the Army Military Police Corps is a subdivision of the Army, which is overseen by the Department of Defense. See Dep’t of the Army, Pamphlet 10-1, Organization of the U.S. Army 2, Fig. 1-1 (1994). And, it appears that the court of appeals correctly concluded that the Depart*212ment of Defense is not a law enforcement agency. See Urrutia, 893 P.2d at 1345-46; Ma, 104 P.3d at 277-78 (adopting the conclusion and reasoning of Urrutia).
However, the common definition of the word “agency” is not bound by bureaucratic happenstance, and we should not construe the word so as to undermine the rationale behind section 16 — 10—103(l)(k). See Guenther, 740 P.2d at 975. An agency is a division of government, and a subdivision of government is, practically speaking, also a division of government. Thus, a subdivision of government is an agency for the purpose of section 16-10-103(l)(k), especially, in our view, when that subdivision is the law enforcement arm of a larger agency. In addition to being a subdivision of government, the Army Military Police Corps is the law enforcement branch of the Army. See Organization of the U.S. Army, supra, App. H: Branches of the Army, at 50. Hence, we conclude that the Army Military Police Corps is an agency.
As to the second question of whether the Army Military Police Corps is a law enforcement agency, the purpose of the Army Military Police Corps is to maintain law and order on Army military bases and installations by enforcing Army regulations and the Uniform Code of Military Justice. See Dep’t of the Army, Pamphlet 600-3-31, Branch Code SI — Military Police (1987); Dep’t of the Army, Field Manual No. 19-10, Military Police: Law and Order Operations (1987). To carry out that purpose, military police officers — including reservists — are trained and authorized to arrest suspected criminals, to investigate crimes, and to detain prisoners. See id. Like civilian police officers, military police officers wear police uniforms, are armed with weapons, and patrol in marked police cars. See id.
Because the duties and responsibilities of a military police officer are analogous to those of a civilian police officer, whose job it is to detect and punish violations of the criminal law, we conclude that the Army Military Police Corps, just like a civilian police department, embodies the common understanding of the phrase “law enforcement.” Therefore, we hold that the Army Military Police Corps is a law enforcement agency for the purpose of section 16-10-103(l)(k) and that an Army military police reservist is a compensated employee of a public law enforcement agency.
IY. Application
Because Ma did not waive his right to make a challenge for cause to a prospective juror who told the court that he is an Army military police reservist, because the trial court should have granted this challenge, and because defense counsel used a peremptory challenge to excuse this prospective juror and subsequently exercised all of Ma’s remaining peremptory challenges, we reverse Ma’s conviction and order a new trial. The judgment of the court of appeals is reversed and the case is returned to that court with instructions to remand it to the trial court for retrial.
Justice COATS dissents, and Justice KOURLIS and Justice RICE join in the dissent.. In its entirety, section 16-10-103(l)(k) provides:
(1) The court shall sustain a challenge for cause on one or more of the following grounds:
(k) The juror is a compensated employee of a public law enforcement agency or a public defender’s office.
. The complete colloquy between the trial court and counsel appears as follows in the trial record:
[DEFENSE COUNSEL]: Judge, I challenge [the prospective juror] for statutory cause. I know we talked about this, and I don’t think there's exact case law, but the statute says if he's a compensated employee of a public law enforcement agency, which he exactly is. He works for a public agency, the United States government, as a police officer. There's nothing in the statute or anything in the case law that says full time or part time. He's a police officer, and I would challenge him pursuant to 16-10-103.
[PROSECUTOR]: Judge, I don't think he comes within that statute. And I know that we've been through this before, and the law is unclear, just like the Court said, just when we thought that we were being clear about what law enforcement is. He is more of a military man than law enforcement.
[TRIAL COURT]: Let me tell you what my concern is. I thought what I intended to be doing when I asked you to approach the bench when [the prospective juror] first said that he was a reservist and was an MP in the reserve was to find out from either of you whether you had a challenge for cause based on his status. What both of you said was, 'We don't have a challenge at this time.' I took that to mean you don't have a challenge based on what you've heard so far but that you obviously wanted to keep your options open in case he said something that would disqualify him for other reasons. So I have concerns about whether this challenge has not been waived. And maybe we just had a miscommunication, but the last thing I wanted to do was to have [the prospective juror] sit around here for five hours and then find out from defense counsel that they now think an MP in the reserves is a member of a law enforcement agency.
[DEFENSE COUNSEL]: Well, Judge, I'd ask the Court to read the record, back because I know that that is what [the prosecutor] said. I'm not sure what I said, but I don't think I said that. That was not my understanding.
[TRIAL COURT]: Well, did you say you had a challenge for cause to [the prospective juror]? [DEFENSE COUNSEL]: To be honest, I can't remember exactly what I said. I think the record can speak for itself.
[TRIAL COURT]: Well, you didn't raise the challenge for cause, did you? And I don’t care about the exact language that was used. I brought you up here [earlier] to find out if either of you had a challenge for cause to [the prospective juror] based on his status as an MP, and neither of you did.... The challenge is denied as waived.
. We granted certiorari on the following question:
Whether the court of appeals erroneously concluded that the trial court properly denied Mr. Ma’s statutory challenge for cause to a juror *209that regularly testified as a military police officer in various cases, including "domestic situations," without addressing the propriety of the trial court’s finding that Mr. Ma waived the challenge.
. Of course, this does not preclude a defendant from obtaining a retrial where the trial court denies a valid challenge for cause after the defendant has used his available peremptory challenges.