The difference between 警察 and 警方?
方 has the meaning of 'side'

警察 can be the collective noun for the entire police force or a singular noun for one policeman.

警方 means '警察方面' (the police side). It can only be a collective noun.

More example:

中國 (China) - 中方 (the Chinese side/ The Chinese government)

日本 (Japan) - 日方 (The Japanese side/ The Japanese government)

中日雙方同意 (Both China's and Japan's government agree)


  In "警方以涉嫌遗弃遗体罪再次逮捕该犯罪嫌疑人。"  '警方' refers to 'the police (department)'