How likely is it to get asked about your job in detail by Immigration?

Is this kind of things common in passing through the immigration?

About five years ago I was visiting the US to attend a conference on plasma physics. After stating this, I got a series of gradually more detailed questions until eventually, to my astonishment, the CBP agent asked me, “How do I derive the Debye length in a plasma?”

This is a very hard technical question (unless you already know the answer) that you would be unlucky get in a PhD exam. He didn’t Google anything; this wasn’t at secondary inspection, that was his instant reply to my statement of purpose of entry.

Was he doing a night school class in plasma physics? Does he spend too much time on Reddit Ask Science? Did he memorise a question for every occupation? Who knows.

That said, this was unusual. 99% of my visits to the USA, as soon as I said I was a researcher, they lost interest in the conversation and stamped me in.

Is there anything that I can do to avoid the situation happens, or at least mitigate the possibility, as a traveler?

Do not assume that the immigration people are clueless. They are certainly allowed to ask probing questions.

(Alternatively, if you are going to lie to immigration in order to gain entry, it might be worth at least studying the basics of your fictional profession.)

Is it […] only for specific types of visa applicants, or maybe is it more related to which passport a travler has?

I was travelling on a British Citizen passport, under the visa waiver program, which normally is great for entering the US.

Immigration can ask anyone about their situation.

Now I wonder it might be better to declare another, more obscure job title such as a tech consultant…

If you represent yourself as a consultant, that just gives the officer more room to ask questions about what exactly you do, who are your clients, who is your employer, that sort of thing.

Lying to immigration is not a good idea. You are setting yourself up here for a long ban.

If you are entering for a job they are likely to ask you about the job. It’s unusual to the point of causing a Twitterstorm to ask technical questions that try to establish you’re qualified for the job (especially since the particular question they asked was so left-field weird) but not to say “how much experience do you have?” or even ask for a copy of your resume.

If you are entering for tourism they may ask what sights you intend to see. If you are entering to visit family they may ask about the family member and your relationship. Same for a friend. If they suspect you’re planning to find a job, they may start asking about what you do. If you have an occupation but no current job, this raises the suspicion that you are coming over to correct this imbalance.

If someone asks you a highly technical question you can’t answer (I can’t balance a tree, though I do know what an abstract class is) there’s really nothing you can do. They can ask you anything, and if they think you’re lying, avoiding their questions, or even are too prepared with snappy answers, they can decline your admission. All you can do is go home and try for better luck next time, either by applying for a visa or by showing up at the border again. This isn’t something you can prep for.

I would say, however, that lying, exaggerating, or otherwise misrepresenting yourself is never wise. If you’re not a Software Developer, why say you are? If you don’t need to work at all, maybe put Retired. Or whatever truly describes you. Unemployed suggests you’re looking for work, so don’t put that. Tell the truth.

Immigration officials sometimes interview people at the border to gauge their reactions. This might happen if they suspect that papers may be forged, or that the traveler is lying. Instead of sending the documents to an expert, they ask a few questions.

• The easiest thing is to ask people for their birthdate and birthplace, while the official has the passport in hand (and the applicant does not).
• There might be small talk about the travel plans. So, you’re going to visit London/New York/Tokyo? Which museums are you going to see?

Going into technical stuff seems little different from that. The immigration official doesn’t even have to be a software engineer, he or she could simply judge if the traveler is rattled by the question, or able to answer confidently. If they dislike the reaction, the suspect papers get examined more closely.

See Strange landing interview at LGW for an EEA national.