In reality, your question is made up of major and minor premises:

A) (Major premise): Is it possible for a person to be a muqallid (follower) in some issues and a mujtahid in some others?

Ijtihad is of two types: absolute and incomplete

One is complete; the jurist who attains this level of ijtihad is called "an absolute mujtahid" - mujtahid mutlaq. Such a mujtahid is capable of deducing legal opinion from its respective source in the different fields of fiqh (jurisprudence). The other is incomplete; the jurist who manages thus far is partially equipped, i.e. having attained ijtihad only in some branches of the shari’a. Thus, he is capable of deducing a limited legal opinion.

This is a discussion concerning legal theories about which there two different opinions [1] :

 1. Ijtihad is the scientific capability of the person to deduce a legal opinion from the whole body of principles of the faith. For this reason, some jurists do not accept partial capability in ijtihad. In fact, they are of the view that mujtahid is a jurist competent enough to deduce precise inferences regarding all issues; he acts upon what in all probability is the law. The correct opinion is that which does not accept partial capability because mujtahid is one who possesses the capability to deduce precise inferences regarding the commandments from the Islamic sources (i.e. the holy Qur'an and the Sunnah of the holy Prophet, peace be upon him and his progeny). Therefore, he should have acquired all the preliminaries of ijtihad i.e. the pre-required sciences. [2]

2. A person who manages partial deduction, since he has attained ijtihad only in some branches of the shari’a or worked on other branches and may have not reached the position to issue a fatwa, is known to be mutajazzi. [3] Thus, a mutajazzi is capable of deducing a limited legal opinion. Many scholars are of the view that attaining ijtihad in some branches of the shari’a is possible but such an ijtihad is valid for the person himself not for others. Therefore, no one can follow him in jurisprudential matters but some jurists say that it is sufficient to follow a mutajazzi. “The verdicts of a mutjazzi who has legal opinions in some branches of fiqh are valid for himself and the permissibility of following him is a matter of objection, although it is not unlikely to be permissible. [4]

B) (Minor premise) Can anybody who conducts a research attain this degree?

As for the second part, which has also something to do with your question, we mention the following points which seem to be necessary and at the same time, we advise you to refer to our website for more information on the same topic.

1. The science of jurisprudence (ilm al-fiqh), like all other vast sciences, has a number of affiliate sciences which serve as a supplement and pre-requisite to this science. They include Arabic literature (etymology, syntax, grammar, rhetoric etc.) commentary, rijal (science of biography), dirayah (contextual study of hadith), principles of jurisprudence (Osul-e fiqh) etc.

2. Ijtihad does not mean seeing and translating a narrative and finally telling others what it means. In fact, all the aforementioned sciences and a few others have a direct or an indirect role in it.

To clarify the answer to your question, we shall produce the following example:

Can a person who has no knowledge of medical science prescribe a medicine for himself or for others simply because he has read the name of the medicine in a book? Given that the book does not seem to be reliable and the author is not known, one cannot prescribe medicines especially when there are certain elements that play a role e.g. the physical condition of a person, the weather etc. Hence, one who considers himself to be capable of inferring shari’a laws must note that ijtihad is not only about understanding and translating the Quranic verses and prophetic traditions. Given the personal details you have provided in your message, you are not a Mujtahid. One of the ways through which you can ascertain whether or not you are a Mujtahid is to refer to a qualified and just Mujtahid and explain to him your understanding and deduction method. If he permits, you can act according to your own understanding and upon your own ijtihad.

For further reading, vide: Ijtihad in Shi’a No.2675; A Brief History of Ijtihad, Rijal, Dirayah and Usul, No.5582 and Discrimination in Taqlid, No.2620 (site:2737).