The death note Light used was returned to the original owner. The Police force does have a death note, but it's locked up and kept under surveillance I got this from Yahoo answers to kinda help:
1. SIDOH's - originally given by ryuk to light, then went to higuchi through rem, then to task force, traded by mello's mafia for sayu, claimed by sidoh, taken back to shinigami world by sidoh.
2. GEALOUS's - taken by rem on gealous's death after saving misa, given to misa by rem, buried in the ground after she gave up ownership, taken out by misa after getting released from surveillance, remained with misa for a long time, given to mikami, got into the hands of near in the end.
3. REM's - actually belonged to rem, taken by light after rem's death, sent to task force in the name of kira through ryuk, remained with task force, carried by Aizawa at the final show down.
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The last death note ultimately ended up in the hands of the task force. If I recall correctly, Sidoh's Death Note was confiscated by the task force after Higuchi was apprehended, but was forfeited during a hostage exchange with Mello.
Misa and Light covertly give Rem's Death Note to the task force after they lose the first one to Mello. This is the Death Note that allowed Soichiro to be granted Shinigami eyes. This Death Note is kept by the task force all the way until the end, but it's kept under lock.
Just hope this kinda helps,
Here's my sourceUPDATE:
Please dont be confused on why Juno is there. There is a reason why I have him in this roleplay, you'll know soon enough.