Since any ices cold enough to contain nitrogen in its original form would also carry rather large amounts of argon and deuterium, Huygens may be able to settle this question by measuring those two gases in Titan's atmosphere. Because of that unique combination of weak gravity and dense atmosphere, Titan's atmosphere towers above its surface to an awesome height with the top of its haze fully 200 km above its surface. It should be kept in mind that, by all indications, Titan has few if any actual clouds - just that smog. But, rarified or not, it's extremely important scientifically, because it's a rich natural laboratory for the synthesis of complex organic molecules of the sort that must have served for the beginning of life's evolution on ancient Earth. Even today we are essentially completely in the dark as to what the individual steps in that process might have been.
Titan also plays an important part in that search.
Moreover, as was first pointed out by Carl Sagan in the early 1990s, there are many individual patches of Titan's surface, around its impact craters, where gigantic meteorite impacts certainly DID produce enough temporary heat to melt the water ice in Titan's surface - and, in fact, to keep some of that water liquid for periods that may sometimes have lasted for thousands of years. Again, this is probably far too short a time for life to have ever evolved on Titan - but it is long enough for a great many additional organic compounds which do contain oxygen to form there, providing us with still more insight into the chemical synthesis processes that must have occurred on ancient Earth. Although the chances that the Huygens probe will happen to land at such a spot are small, they will be the single most important target for the next Titan probes, which will actually be able to travel across and survey its surface by driving or flying. And Huygens may still be able to find some such compounds mixed in with the general surface. The Sun's and Saturn's radiation should also, over the eons, slowly turn its methane into the slightly more complex hydrocarbon ethane - enough to form a layer of liquid ethane several hundred meters deep over Titan's surface.