In the following sentence, should I use who or whom? It is highlighted in bold.

For instance, Figure 1.1 depicts an operating smart surveillance system, detecting pedestrians whom are crossing dangerous regions, cars in parking lots, and ships.

I think it should be whom because the "operating smart surveillance system" is the subject, while "pedestrians" are the object. But, my professor corrected it to who and now I'm not sure.

  • 6
    The relative clause should start with who: "X are crossing regions". Regions: object. X: subject. But it's good that you've explained your reasoning. Jan 19, 2015 at 21:06

2 Answers 2


The system is subject but then the next clause talks about pedestrians who also become subject crossing the regions etc. Removing the pronoun itself will also work.

A quick trick!

Now, cut off the sentence.

Pedestrians whom are crossing [something]

Here only, we get a hint that it seems incorrect.

Now, think that it's about 'you'. If 'I' fits, put 'who' and if 'me' fits, put 'whom'.

me I am crossing [something]

Technically, if the pronoun in question is doing something, prefer putting 'who' (what they call subject) and if it's receiving something, prefer 'whom' (what they call object)!

  • An even easier way to remember it, since they both either end in 'm' or a vowel, is "whom" goes where "him" would go, and "who" goes where "he" would go.
    – Kevin
    Aug 31, 2015 at 3:30

Pedestrians is the subject of the sub-clause "pedestrians who are crossing...". I think the professor is right.

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