There were three thefts in the grocery store in the month of February, May, and July 2020. The security camera recorded the video and the four suspects were in every video as shown in the picture below.
The detective Conan tried to have a closer look and suddenly notice one detail and everything became clear.
What did he notice?
Who was the thief?
The pregnant lady.
The detective Conan noticed that the pregnant women look 6-7 months pregnant in January, May, and even in July. So that pregnant lady is the thief we are looking for and must be faking her pregnancy.