Let's take a page from Silverman's book, VII.3. Let $\mathfrak{p}$ be one of the primes of good reduction of $A$. Let $K/k$ be any extension, and let $\mathfrak{P}$ be a prime of $K$ above $\mathfrak{p}$. The reduction map $A(K)\to A(\mathcal{O}_K/\mathfrak{P})$ becomes injective when you restrict to torsion points of order prime to the residue characteristic of $\mathfrak{p}$ -- this is proved using an appeal to formal groups.
Now choose two such primes $\mathfrak{p}$ and $\mathfrak{p}'$ with distinct residue characteristics. Convince yourself that there exists a $K/k$ and primes $\mathfrak{P},\mathfrak{P}'$ of $K$ for which $A(K)\to A(\mathcal{O}_K/\mathfrak{P})\times A(\mathcal{O}_K/\mathfrak{P})'$ A(\mathcal{O}_K/\mathfrak{P}')$has nontrivial kernel. Nontrivial points in the kernel must not be torsion. 1 Let's take a page from Silverman's book, VII.3. Let$\mathfrak{p}$be one of the primes of good reduction of$A$. Let$K/k$be any extension, and let$\mathfrak{P}$be a prime of$K$above$\mathfrak{p}$. The reduction map$A(K)\to A(\mathcal{O}_K/\mathfrak{P})$becomes injective when you restrict to torsion points of order prime to the residue characteristic of$\mathfrak{p}$-- this is proved using an appeal to formal groups. Now choose two such primes$\mathfrak{p}$and$\mathfrak{p}'$with distinct residue characteristics. Convince yourself that there exists a$K/k$and primes$\mathfrak{P},\mathfrak{P}'$of$K$for which$A(K)\to A(\mathcal{O}_K/\mathfrak{P})\times A(\mathcal{O}_K/\mathfrak{P})'\$ has nontrivial kernel. Nontrivial points in the kernel must not be torsion.