The Latin legal term "ignoramus" is present within legal dictionaries for when there is not sufficient evidence. Are terms like this still used, or does a jury resort to plain English when endorsing a bill and use "not found" in the place?
However, in Australia there has been a dedicated push to reduce the use of Latin terms to those that have entered the general English vernacular or that refer to specific procedures in the legal system.
So it’s OK for a lawyer to use de facto or certiorari but frowned upon (as in, the judge will usually say “In English, please”) to use de die in diem.
Latin Terms Used In English Legal Terminology
I have never seen the specific Latin legal term ignoramus used in American legal jurisprudence.
But, all sorts of Latin and Latin derived legal terms are common in American legal jurisprudence and probably even more common in English and European jurisprudence (and, of course, Latin is still the primary language of Roman Catholic canon law, a discipline that still have active practitioners, even in 21st century Denver, Colorado).
Here are 112 common examples that I see used regularly in the law (some or all are arguable English loan words rather than true direct uses of foreign terminology from a linguistic perspective, others are arguably not specifically legal in nature). Sometimes true loan words persist because the "plain English" preferred substitutes are less widely understood or have a meaning less well established in precedent.
per diem (the amount of interest that accrues per day, also a lump sum allowance per day for out of pocket expenses in lieu of reimbursement based upon receipts).
nolo contedre (no contest to criminal charges)
ab initio (anew from the beginning)
a priori (in advance)
ad infinitum (and so on forever)
affidavit (a sworn statement)
arguendo (for sake of argument)
caveat emptor (buyer beware)
alter ego (disguised secondary identity)
ad hominem (an attack on the person making an argument rather than the argument itself)
ceteris paribus (all other things being equal)
de novo (without deference to previous proceedings or decisions)
dictum (statements of law made when not necessary to resolve the present case that are not precedents for case law purposes)
stare decisis (the doctrine that precedent should be followed by courts)
subpoena duces tecum (a legal document demanding the production of documents or things)
erratum (a list of error corrections)
et seq. (abbreviation of et sequens, meaning "and the following ones". Used in citations to indicate that the cited portion extends to the pages following the cited page.)
in extremis (in extreme circumstances)
in flagrante delicto (caught in the act)
mittimus (the written statement of a finally determined criminal sentence)
in forma pauperis (as a poor person with a request for a waiver of fees)
in rem (limited to or pertaining to property)
in pari delicto (having joint responsibility)
in pari materia (to be interpreted together with other parts of the same source material)
in re (in the matter of)
in situ (in place)
status quo (the pre-dispute or pre-event or current state of things)
jurat (the portion of a notarization containing the oath or acknowledgement itself)
lacunae (unaddressed point or issue)
lex loci (jurisdiction by virtue of the location)
lis pendens (notice of pending litigation, usually recorded in real estate records)
N.B. (abbreviation for "nota bene" meaning "note well").
per capita (per person)
per stirpes (per line of inheritance)
per curiam (by the court as a whole without attribution of authorship)
per se (something that is automatically or definitionally true)
pro forma (for form, sometimes financial projections estimated since they anticipate the future)
inter vivos (during life, usually in relation to a gift or a trust)
C.V. (abbreviation for "curriculum vitae" which is a resume of a learned professional such as an expert witness, or scholar).
pro tem (temporarily)
quantum meruit (an amount owed notwithstanding a lack of a contract)
quasi (similar to but not the same as)
res (the thing, often referring to the assets of a trust)
sua sponte (without prompting and without a request for action)
sub nomine (under the name of, usually used when there is a name change in mid-litigation)
sub silentio (a ruling or agreement made without explicitly saying so)
supersedeas (a bond offered in lieu of other remedies)
ultra vires (beyond the authority of the person acting)
veto (refuse to allow to go forward)
vice versa (the other way around, i.e. in reverse order)
viz. (abbreviation of "videlicet" which means "namely")
subpoena (a order to testify at a time and place)
modus operandi (distinctive customary or habitual technique)
in personam (acting on or imposing obligations upon a person)
forum non conveniens (a doctrine providing that a court may decline to hear a case over which it technically has jurisdiction because there is another more convenient forum in which to hear the dispute).
nunc pro tunc (retroactively to the relevant date)
et cetera (abbreviated etc., meaning and so on).
ad valorem (in proportion to value, usually for property taxes)
ad hoc (in response to the circumstances rather than as part of a plan)
amicus curiae (a brief filed in a case by a non-party as a friend of the court)
guardian ad litem (a guardian of a litigant for purposes of litigation)
actus reus (the act which must be taken to commit a crime or tort)
bona fide (genuine, often in the sense of not acting as a straw man, not aware of wrongdoing, and not acting on behalf of an interest part)
alibi (the defense of being somewhere other than where a crime or act was committed at the time)
corpus delicti (the facts showing that a crime was committed)
res ipsa loquitor (a doctrine that presumes liability in cases where control of the proof is predominantly with the alleged tortfeasor)
res judicata (a doctrine that bars re-litigation of civil disputes)
pro se (representing oneself without a lawyer)
pro hoc vice (a lawyer temporarily licensed outside his or her jurisdiction of admission for a particular case)
pro bono (free legal representation)
a fortiori (something is true in the stronger case because it is true in the weaker case)
testator (male or person who writes a will)
testatrix (female who writes a will)
executor (male or person who administers a probate estate)
executrix (female who administers an estate)
ipse dixit (a statement that is true solely by decree rather than with justification)
mens rea (intent)
scienter (specific knowledge of one's own wrongdoing)
mea culpa (a concessionary or appeasing confession or admission)
in limine (a motion when brought on the eve of trial to adjudicate evidence issues)
in loco parentis (in the place of a parent)
de facto (in reality)
de jure (as a matter of law)
certiorari (discretionary supervisory review of an inferior tribunal or quasi-judicial body)
quo warranto (an action to determine the validity of an appointment)
mandamus (a action to order a public official to take a non-discretionary action)
habeas corpus (a suit over who should have custody of a human being, usually an adult detained by the government on criminal or terrorism charges)
ex post facto (having retroactive effect)
ex post (after the fact)
ex ante (pre-dispute, before the fact)
ex parte (action in court or communications with a judge outside the presence of the adverse party)
in camera (private review by the judge without allowing review by all interested parties).
sine die (termination of a session, usually of the legislature, without an intent to reconvene in the same session)
ipso facto (by definition or by virtue of holding a position)
nexus (a legally relevant connection)
post mortem (after death)
prima facie (proof that is sufficient if not contradicted by other evidence)
quid pro quo (one thing in exchange for another, a direct barter)
inter alia (among other things)
ibid (abbreviated "id.") (same citation as the previous one used).
et al. (an abbreviation for et alia (neuter plural). But it can also be an abbreviation for et alii (masculine plural), or et aliae (feminine plural). This phrase means “and others.")
i.e. (abbreviation for id est, meaning “that is")
e.g. (abbreviation for the Latin phrase exempli gratia, meaning “for example.”)
Terms From Other Languages
A few legal terms that are loan words are not directly Latin in origin. For example:
replevin (a lawsuit to recover physical possession of tangible personal property, from Old French).
Yiddish is not infrequently used in American legal writing, although rarely as a term of art. More frequently it is used to add colloquial color to legal writing.