VAUGHN, Resident Judge.

ORDER

Upon consideration of the defendant's motion to suppress, the state's opposition, and the record of the case, it appears that:

1. The defendant, Michael N. Clay, is charged with driving under the influence of alcohol in violation of 21 Del. C. § 4177. He has filed a motion to suppress the result of the intoxilizer test. In support of his motion, he contends that his initial detention was not a valid traffic or investigatory stop, and that even if it was, there was no probable cause to arrest him for driving under the influence. The state disputes these contentions.

2. The evidence presented at a hearing on the motion established the following facts. Sometime in the evening of September 19, 2001, the Delaware State Police received a call of a "physical domestic" incident at a residence on Fox Hunter's Road near Harrington. Troopers responded but found no one at home. Later, at about 3:30 a.m. on September 20, the defendant called the troop barracks inquiring as to whether the police had found his wife. He indicated that he was on his way from Maryland to the residence on Fox Hunter's Road, looking for his wife. He mentioned that he had been drinking, and it sounded to the officer taking the call like he had been drinking. Trooper Mark Ryde was dispatched to the Fox Hunter's Road address to follow up on the domestic incident complaint. On his way, he came up behind a vehicle which turned out to be the defendant's. He remained behind the vehicle for about two minutes until it turned into the driveway of the Fox Hunter's Road residence which was the subject of the domestic incident. During the time he was behind the defendant's vehicle, he did not observe any irregular driving, other than the fact that on one occasion the left wheels of the vehicle crossed the double yellow line in the center of the road. The vehicle, however, immediately corrected itself back to its lane of travel. As the officer followed, he had the tag checked out and learned that the vehicle was registered to Karen Clay. When the defendant pulled into the driveway, the officer pulled behind and turned on the overhead lights of the police cruiser. By then the defendant had exited his vehicle. The officer approached and noticed that the defendant swayed a little to the left and right. When the officer got close enough to engage in conversation, about three or four feet, he detected an odor of alcohol on the defendant's breath. He also noticed that his eyes were watery and glassy and appeared slightly bloodshot. The officer asked the defendant about the domestic incident, where his wife was, and also whether he had been drinking. The defendant said that he had been drinking at a beef and beer hosted by his boss. The officer then began to go through standard field sobriety tests for a person who might be under the influence. According to the officer's testimony, his decision to proceed with field tests was based upon the fact that the defendant had an odor of alcohol, had admitted drinking, had watery, glassy, bloodshot eyes, had crossed the double yellow line on the one occasion, and had swayed when he got out of the car. Since the defendant said he had only an eighth grade education, the officer did not administer an alphabet or counting test. The defendant also said he had a disability. Therefore, the officer decided not to do the one-leg stand or the nine-step walk and turn test. The officer did administer the horizontal gaze nystagmus test after determining that the defendant did not wear glasses or contact lenses. At the hearing the officer explained his training with regard to that test, and explained the test itself in some detail. It was clear that the officer was well-qualified to administer the test. He explained that while administering the test, one looks for six clues. In the defendant's case, all six clues were present. The officer then administered a portable breath test, using the Alco-Sensor III, which the defendant failed. The officer then placed him under arrest for driving under the influence. Later, at the police station, the defendant was given the intoxilizer test which is the subject of this motion.

3. The defendant contends that he was detained at the point where the officer pulled in behind him and activated his police lights; that before a person can be detained an officer must have a "reasonable and articulable suspicion" that the person has engaged in some criminal activity; that the officer did not have a reasonable and articulable suspicion that the defendant was driving under the influence prior to the detention; that the officer did not have a reasonable and articulable suspicion that the defendant had committed a crime in connection with the domestic incident; and that the initial detention, therefore, was not a valid stop under 11 Del. C. § 1902 and violated his right to be free from an unreasonable search or seizure under the state and federal constitutions. He further contends that even if the initial detention was justified, the officer did not have probable cause to believe that he had been driving under the influence. Therefore, the result of the intoxilizer test administered at the police station must, he contends, be suppressed.

4. The Court agrees that the defendant was detained at the point where the officer pulled in behind him and activated his police lights. A detention occurs "when the officer, by means of physical force or show of authority, has in some way restrained the liberty" of an individual. The focus is on whether a reasonable person in the defendant's place would have believed that he was not free to ignore a police presence and go about his business. Here, the officer's act of pulling in behind the defendant and turning on his police lights was a detention. In fact, the officer testified at the hearing that the defendant was not free to go at that point.

5. The next issue is whether the officer had "a reasonable and articulable suspicion" that the defendant was involved in criminal activity when the detention occurred. An individual can be detained only when such suspicion exists. To determine whether a "reasonable and articulable" suspicion of criminal activity exists, one must examine the totality of the circumstances "as viewed through the eyes of a reasonable, trained police officer in the same or similar circumstances, combining objective facts with such an officer's subjective interpretation of those facts."

6. The state contends that the officer had a reasonable and articulable suspicion to believe that the defendant was driving under the influence. It argues that the fact that the defendant admitted when he called the troop that he had been drinking, that it sounded over the phone that he had been drinking, and that he committed a traffic "violation" when he crossed over the center line and then came back, rise to the level of a reasonable and articulable suspicion of such. However, I am not persuaded that the Court should find, on the record of this case, that the officer had a reasonable and articulable suspicion that this defendant was driving under the influence prior to the detention in the driveway. The state argues that crossing the centerline was a violation of 21 Del. C. § 4122(1) which prohibits a vehicle from moving from its lane of travel unless such movement can be made with safety. I do not believe that an act of briefly drifting across the centerline which is immediately corrected, in and of itself, is a violation of this statute, or could create a reasonable suspicion that a motorist was driving under the influence. The fact that when the defendant called the police he admitted to drinking, and sounded like he had been drinking, however, is more significant. It could be argued that when the police receive a call from a motorist who says he has been drinking, and the police perceive over the phone that drinking has impaired his speech, the police have a duty to dispatch a patrol trooper to investigate that driver. From the record of this case, however, it is not at all clear that the officer knew that the car in front of him was being driven by the defendant prior to the detention in the driveway. The vehicle was registered to Karen Clay. In addition, the officer testified that he didn't pull into the driveway to investigate a DUI. He did so to investigate the domestic incident. The officer's explanation of his actions was as follows:

. . . when I pulled up and put my lights on, if he decided to leave, would I have detained him? The answer is yes.

My initial response to that residence wasn't for a driving under the influence driver. We were there earlier for a — some type of physical domestic that, when the troopers arrived, both parties had left.

We subsequently got a phone call from Mr. Clay saying that he was coming back into Maryland looking for his wife. We have to follow up on all domestics. For all we knew, the female — we had no contact. She could have been laying somewhere . . . .

On this record I do believe, however, that the officer was justified in detaining the defendant, at least briefly, to investigate the domestic incident. A report of a "physical domestic" incident creates a reasonable and articulable suspicion that some criminal activity has occurred, if only an offensive touching. In this case the wife was missing. The officer had no other information. Under these circumstances, I find that the officer had a reasonable and articulable suspicion of criminal activity involving the husband to justify a brief, investigatory stop.

7. The next issue is whether the officer had probable cause to make an arrest for driving under the influence. The term probable cause connotes less evidence than that which would justify a conviction. Only a probability, and not a prima facie showing, is the standard of probable cause. Probable cause is determined not by precise standards, but by the totality of the circumstances. Probable cause is an elusive concept which avoids precise definition, but lies somewhere between suspicion and sufficient evidence to convict.

8. In this case the information available to the officer was that the defendant admitted he had been drinking, swayed upon exiting his vehicle, exhibited an odor of alcohol from about three feet away, had watery, glassy and slightly bloodshot eyes, showed six clues on the horizontal gaze nystagmus test and failed the portable breath test. The defendant argues that the portable breath test should be given no weight because the Alco-Sensor III had not been calibrated according to manufacturer's specifications. Those specifications recommend that the unit's calibration be tested weekly for a period of one month after initially being placed in service, with monthly calibration testing thereafter. The specifications also note, however, that the unit will generally hold its calibration for months. In this case, the unit was placed in service in May or June of 2001, about four months before the defendant's arrest. The officer testified that he was not aware that the unit's calibration had been tested at all. Since the officer was unable to testify that the unit had been calibrated at all since being placed in service, I tend to agree that it should be given little weight. The defendant also argues that the horizontal gaze nystagmus test should be given no weight because, although the officer testified that he found six clues, he never testified as to whether the presence of six clues is a pass or a fail. While it is true that the officer never testified expressly that finding six clues meant that the defendant failed the nystagmus test, he testified that he "checks for" six clues, and I infer that the presence of all six is evidence that an individual is under the influence.

9. Applying the standard of probable cause set forth above, I find that the admission of drinking, swaying upon exiting the vehicle, an odor of alcohol from three feet away, watery, glassy and slightly bloodshot eyes, and the presence of all six clues during the nystagmus test, are sufficient to establish that the officer had probable cause to believe the defendant was driving under the influence.

10. Therefore, the defendant's motion to suppress is denied.

IT IS SO ORDERED.