You can remember the meaning of 嫌疑人 with this easy mnemonic:
I dislike (嫌) almost everyone, and I doubt (疑) there is even one man (人) in this world who doesn't dislike me back, especially that suspect I arrested earlier today who turned out to be innocent.
Using mnemonics to remember the meaning of Chinese characters like can have an enormous impact on how long to learn Mandarin it takes.