The derivative suffix –siz denotes negation. It is a productive suffix which means that you can add it to just about any noun (or pronoun) and you will be understood and its use is not limited to certain contexts or words.

-siz makes

1. adjectives: parasız ‘penniless, free of charge’, eşsiz ‘unequalled’, sınırsız ‘unlimited’

2. adverbs: arabasız ‘without a car’, parasız ‘free of charge’, sensiz ‘without you’

3. nouns: telsiz ‘a wireless device’, Hamursuz ‘passover, the Jewish Easter’

Why are police officers called aynasız in slang?

inançlı = believer of islam

inatçı = stubborn

There are many stories about why they are called aynasız but they are far from the truth..  

I think* they are aynasız because they are asık suratlı, asabi..   

ayna- mirror/ (surface) parlak, pürüzsüz.. 

aynalı - mirrored/ (thing) parlak yüzeyli, güzel; (person) güzel/gülümseyen yüzlü, 

aynasız - (thing) soluk, donuk; (person) asık suratlı, asabi

*nobody has to agree with me on this

If my memory doesn´t trick me.. I explained it to you some months ago..

Kimsenin bu kitabı okumadığını (-) sanıyorum (+) => (-) kimse okumamış olmalı

Kimsenin bu kitabı okumadığını (-) sanmıyorum (-) => (+) herkes okumuş olmalı

Well, thank you for your patience, scalpel.

Your explanation of aynasız ´cop´ was in line with grammar. -siz is often the opposite of -li. But when I asked I was expecting something more...colorful.

When the meaning ‘without’ is added to a verb there are two options:

1. –mek|siz|in

The derivation suffixes –li and –siz often make oppositions. When added to verbal nouns, though, the old intstrumental case ending –n is added to –siz.

İnsan ağlamaklı oluyor vallahi. ‘One feels like crying.’

Hiçbir akşam ağlamaksızın yatağımda yatamam. ‘I can’t go to sleep any evening and not cry.’

2. –meden

I always thought this is a combination of infinitive marking and dative ending but historically it is not. Lewis says the oldest occurances of this form are the type –meti where the first syllable was probably the negative –me-! With the adding of the instrumental case it became -metin and the end of it was confused with ablative. (It has been mentioned here also http://www.turkishclass.com/forumTitle_51754.)

Ne olur ağlamadan ayrılalım. ‘Please, let’s part without crying.’

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Maybe the misunderstanding of the above structure has made me combine ablative case with negation. Oh, but now I remembered another example:

Allah kimseyi hardaldan etmesin. ‘Allah, don’t leave anyone without mustard.’ (Orhan Veli Kanık)