Answer:
The apostrophe should be placed right after the final -s in "newspapers".
Step-by-step explanation:
The apostrophe is used to show possession. With singular nouns, you should add an apostrophe plus the letter -s (see 1). With plural nouns, you should only add an apostrophe after the -s (see 2). In the sentence above, the plural noun "newspapers" lacks the apostrophe, so the possession relationship between newspapers and witnesses is not grammatically shown.
1) A woman's dress
2) Guys' night out